discharge tube experiment by jj thomson

Towards the end of the 19th century Joseph J.Thomson (1856-1940) was studying electric discharges at the well-known Cavendish laboratory in Cambridge, England. Several people had been studying the intriguing effects in electric discharge tubes before him. Spectacular glows could be observed when a high voltage was applied in a gas volume at low pressure. It was known that the discharge and the glow in the gas were due to something coming from the cathode, the negative pole of the applied high voltage. Thomson made a series of experiments to study the properties of the rays coming from the cathode. He observed that the cathode rays were deflected by both electric and magnetic fields - they were obviously electrically charged. By carefully measuring how the cathode rays were deflected by electric and magnetic fields, Thomson was able to determine the ratio between the electric charge (e) and the mass (m) of the rays. Thomson's result was

e/m = 1.8 10-11 coulombs/kg.

The particle that J.J.Thomson discovered in 1897, the electron, is a constituent of all the matter we are surrounded by. All atoms are made of a nucleus and electrons. He received the Nobel Prize in 1906 for the discovery of the electron, the first elementary particle.

Dalton's Model of the Atom / J.J. Thomson / Millikan's Oil Drop Experiment / Rutherford / Niels Bohr / DeBroglie / Heisenberg / Planck / Schrödinger / Chadwick

Plum Pudding

J.J. Thomson

by: Ann Johnson

• 1.1 Biography
• 2 Electron Discovery
• 3 Cathode Ray Experiments
• 4 Isotopes and Mass Spectrometry
• 5.1 Further reading
• 5.2 External links
• 6 References

The Main Idea

J. J. Thomson was a Nobel Prize winning English physicist who used cathode rays to discover electrons. He also developed the mass spectrometer.

J. J. Thomson was born on December 18th, 1856 in England. His father wished he would become an engineer, however he could not find an apprenticeship. He attended Trinity College at Cambridge, and eventually headed the Cavendish Laboratory. Thomson married one of his students, Rose Paget, in 1892. They had two children, Joan and George Thomson. George eventually became a physicist and earned a Nobel Prize of his own. J. J. Thomson published over 200 papers and 13 books. He died on August 30th, 1940 in Cambridge and is buried in Westminster Abbey.

Electron Discovery

J. J. Thomson discovered the electron in 1897 while performing experiments on electric discharge in a high-vacuum cathode ray tube. He interpreted the deflection of the rays by electrically charged plates and magnets as "evidence of bodies much smaller than atoms." He later suggested that the atom is best represented as a sphere of positive matter, through which electrons are positioned by electrostatic forces.

Cathode Ray Experiments

A cathode ray tube is a glass tube with wiring inserted on both ends, and as much air as possible pumped out of it. Cathode rays were discovered to travel in straight lines, just like waves do. Physicists knew that the ray had an electric charge, and they were trying to figure out if that electric charge could be separated from the ray.

Thomson had the hypothesis that the ray and charge were inseparable, and designed experiments using a magnetic field to prove this was true. He first built a cathode ray tube with a metal cylinder at the end. The cylinder had slits in it that were attached to electrometers, that could measure electric charges. When he applied a magnetic field across the tube, no activity was recorded by the electrometers. This meant the charge had been bent away by the magnet. This proved his theory that the charge and the ray were inseparable.

Isotopes and Mass Spectrometry

After discovering the electron, Thomson started studying positive rays. Positive rays behaved very differently from cathode rays, and he found that each ray followed its own parabolic path based on its detection on the photographic plate. He reasoned that no two particles would follow the same path unless they possessed the same mass-to-charge ratio. He correctly suggested that the positively charged particles were formed by the loss of an electron (isotopes). This created the field of mass spectrometry, which is still used very heavily today.

Properties of matter, including mass and charge, are related to Thomson's work with electrons and the mass spectrometer.

Further reading

Thomson, J. J. (June 1906). "On the Number of Corpuscles in an Atom". Philosophical Magazine 11: 769–781. doi:10.1080/14786440609463496. Archived from the original on 19 December 2007. Retrieved 4 October 2008. Leadership and creativity : a history of the Cavendish Laboratory, 1871 - 1919

External links

http://www.cambridgenetwork.co.uk/news/cambridge-physicist-is-streets-ahead/

http://thomson.iqm.unicamp.br/thomson.phphttp://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx http://www.biography.com/people/jj-thomson-40039 http://study.com/academy/lesson/jj-thomsons-cathode-ray-tube-crt-definition-experiment-diagram.htmlhttps://explorable.com/cathode-ray-experiment

[[Category:Notable Scientists]

Navigation menu

By Rupert Cole on 18 December 2013

Jj thomson's cathode-ray tube.

Rupert Cole celebrates JJ Thomson’s birthday with a look at one of the star objects in our  Collider exhibition.

https://www.youtube.com/watch?v=3oNQ_-iLgmA

Holding the delicate glass cathode-ray tube in my hands, once used by the great physicist JJ Thomson , was an incredible treat, and an experience I will never forget.

I had read lots about Thomson’s famous experiments on the electron – the first subatomic particle to be discovered – but to actually see and touch his apparatus myself, to notice the blackened glass and the tube’s minute features that are omitted in books, brought the object to life. History suddenly seemed tangible.

Using more than one cathode-ray tube in 1897 for his experiments, Thomson managed to identify a particle 1,000 times smaller than the then known smallest piece of matter: a hydrogen atom. Cambridge’s Cavendish Laboratory , where Thomson spent his scientific career, also has an original tube in its collection.

Each tube was custom-made by Thomson’s talented assistant, Ebenezer Everett, a self-taught glassblower. Everett made all of Thomson’s apparatus, and was responsible for operating it – in fact, he generally forbade Thomson from touching anything delicate on the grounds that he was “exceptionally helpless with his hands”.

The quality of Everett’s glassblowing was absolutely crucial for the experiments to work.

Cathode-rays are produced when an electric current is passed through a vacuum tube. Only when almost all the air has been removed to create a high vacuum – a state that would shatter ordinary glass vessels – can the rays travel the full length of the tube without bumping into air molecules.

Thomson was able to apply electric and magnetic fields to manipulate the rays, which eventually convinced the physics world that they were composed of tiny particles, electrons, opposed to waves in the now-rejected ether.

Find out more about Thomson and the story of the first subatomic particle here , or visit the Museum to see Thomson’s cathode-ray tube in the Collider  exhibition. If you’re interested in the details of how Thomson and Everett conducted their experiments visit the Cavendish Lab’s outreach page here .

• Foundations
• Write Paper

Search form

• Experiments
• Anthropology
• Self-Esteem
• Social Anxiety

Cathode Ray Experiment

The electric experiment by j.j. thomson.

J. J. Thomson was one of the great scientists of the 19th century; his inspired and innovative cathode ray experiment greatly contributed to our understanding of the modern world.

This article is a part of the guide:

• Ben Franklin Kite
• Physics Experiments
• Brownian Movement

Browse Full Outline

• 1 Physics Experiments
• 2 Ben Franklin Kite
• 3 Brownian Movement
• 4 Cathode Ray Experiment

Like most scientists of that era, he inspired generations of later physicists, from Einstein to Hawking .

His better-known research proved the existence of negatively charged particles, later called electrons, and earned him a deserved Nobel Prize for physics. This research led to further experiments by Bohr and Rutherford, leading to an understanding of the structure of the atom.

What is a Cathode Ray Tube?

Even without consciously realizing it, most of us are already aware of what a cathode ray tube is.

Look at any glowing neon sign or any ‘old-fashioned’ television set, and you are looking at the modern descendants of the cathode ray tube.

Physicists in the 19th century found out that if they constructed a glass tube with wires inserted in both ends, and pumped out as much of the air as they could, an electric charge passed across the tube from the wires would create a fluorescent glow. This cathode ray also became known as an ‘electron gun’.

Later and improved cathode ray experiments found that certain types of glass produced a fluorescent glow at the positive end of the tube. William Crookes discovered that a tube coated in a fluorescing material at the positive end, would produce a focused ‘dot’ when rays from the electron gun hit it.

With more experimentation, researchers found that the ‘cathode rays’ emitted from the cathode could not move around solid objects and so traveled in straight lines, a property of waves. However, other researchers, notably Crookes, argued that the focused nature of the beam meant that they had to be particles.

Physicists knew that the ray carried a negative charge but were not sure whether the charge could be separated from the ray. They debated whether the rays were waves or particles, as they seemed to exhibit some of the properties of both. In response, J. J. Thomson constructed some elegant experiments to find a definitive and comprehensive answer about the nature of cathode rays.

Thomson’s First Cathode Ray Experiment

Thomson had an inkling that the ‘rays’ emitted from the electron gun were inseparable from the latent charge, and decided to try and prove this by using a magnetic field.

His first experiment was to build a cathode ray tube with a metal cylinder on the end. This cylinder had two slits in it, leading to electrometers, which could measure small electric charges.

He found that by applying a magnetic field across the tube, there was no activity recorded by the electrometers and so the charge had been bent away by the magnet. This proved that the negative charge and the ray were inseparable and intertwined.

Thomson's Cathode Ray Second Experiment

Like all great scientists, he did not stop there, and developed the second stage of the experiment, to prove that the rays carried a negative charge. To prove this hypothesis, he attempted to deflect them with an electric field.

Earlier experiments had failed to back this up, but Thomson thought that the vacuum in the tube was not good enough, and found ways to improve greatly the quality.

For this, he constructed a slightly different cathode ray tube, with a fluorescent coating at one end and a near perfect vacuum. Halfway down the tube were two electric plates, producing a positive anode and a negative cathode, which he hoped would deflect the rays.

As he expected, the rays were deflected by the electric charge, proving beyond doubt that the rays were made up of charged particles carrying a negative charge. This result was a major discovery in itself, but Thomson resolved to understand more about the nature of these particles.

Thomson's Third Experiment

The third experiment was a brilliant piece of scientific deduction and shows how a series of experiments can gradually uncover truths.

Many great scientific discoveries involve performing a series of interconnected experiments, gradually accumulating data and proving a hypothesis .

He decided to try to work out the nature of the particles. They were too small to have their mass or charge calculated directly, but he attempted to deduce this from how much the particles were bent by electrical currents, of varying strengths.

Thomson found out that the charge to mass ratio was so large that the particles either carried a huge charge, or were a thousand times smaller than a hydrogen ion. He decided upon the latter and came up with the idea that the cathode rays were made of particles that emanated from within the atoms themselves, a very bold and innovative idea.

Later Developments

Thomson came up with the initial idea for the structure of the atom, postulating that it consisted of these negatively charged particles swimming in a sea of positive charge. His pupil, Rutherford, developed the idea and came up with the theory that the atom consisted of a positively charged nucleus surrounded by orbiting tiny negative particles, which he called electrons.

Quantum physics has shown things to be a little more complex than this but all quantum physicists owe their legacy to Thomson. Although atoms were known about, as apparently indivisible elementary particles, he was the first to postulate that they had a complicated internal structure.

Thomson's greatest gift to physics was not his experiments, but the next generation of great scientists who studied under him, including Rutherford, Oppenheimer and Aston. These great minds were inspired by him, marking him out as one of the grandfathers of modern physics.

• Psychology 101
• Flags and Countries
• Capitals and Countries

Martyn Shuttleworth (Sep 22, 2008). Cathode Ray Experiment. Retrieved Sep 26, 2024 from Explorable.com: https://explorable.com/cathode-ray-experiment

You Are Allowed To Copy The Text

The text in this article is licensed under the Creative Commons-License Attribution 4.0 International (CC BY 4.0) .

This means you're free to copy, share and adapt any parts (or all) of the text in the article, as long as you give appropriate credit and provide a link/reference to this page.

That is it. You don't need our permission to copy the article; just include a link/reference back to this page. You can use it freely (with some kind of link), and we're also okay with people reprinting in publications like books, blogs, newsletters, course-material, papers, wikipedia and presentations (with clear attribution).

Want to stay up to date? Follow us!

Save this course for later.

Don't have time for it all now? No problem, save it as a course and come back to it later.

Footer bottom

• Privacy Policy

• Subscribe to our RSS Feed
• Like us on Facebook
• Follow us on Twitter

• X (Twitter)

Discovery Of Electron | Discharge Tube Experiment

Discharge tube.

The discharge tube is a glass tube having two electrodes sealed into it connected to a vacuum pump to reduce the pressure of the gas taken into it. A slit is placed in the tube to get a sharp beam of radiations.

Experiment:

William Crooks a British scientist studied the passage of electricity through gases taken at different pressures in the gas discharge tube. He observed that air taken in the gas discharge tube at ordinary pressure did not allow the electricity to flow, even when a source of high potential of about 5000 Volt was used. However, when pressure of air was reduced by removing most of the air from the discharge tube then it allowed the current to flow and emitted light (as in neon sign). When pressure was reduced further to about 0.01 torr, then emission of light by air ceased. But the current still flows between the electrodes and produced fluorescent on striking the glass walls opposite to the cathode. This was the result of rays emitted by cathode . Rays emitted by cathode when electricity is passed through a gas taken in the discharge tube at very low pressure are called cathode rays.

Discovery of electron

Emission of cathode rays does not depend on the nature of the electrodes or the gas used in the discharge tube. This indicates that cathode rays (i.e., electrons) are the constituents of all types of matter.

Conclusion:

J.J. Thomson calculated the mass of cathode rays. He suggested that these rays are matter and not electromagnetic radiations. He proposed the name corpuscles for these particles. But as these particles were similar to the particles present in on the electricity, therefore, later on they were named electrons. J.J. Thomson won the 1906 Nobel Prize.

Related Posts

What is A Petri Dish in chemistry is Used For?

What is Solvent in Chemistry?

Buffer Solutions: Henderson’s Equation

Write a comment cancel reply.

Save my name, email, and website in this browser for the next time I comment.

Type above and press Enter to search. Press Esc to cancel.

Privacy Overview

Subscribe to our newsletter below to get regular updates on free Chemistry Resources.

No thanks, I’m not interested!

PhysicsOpenLab Modern DIY Physics Laboratory for Science Enthusiasts

Cathode ray tube experiments.

April 18, 2017 English Posts , Quantum Physics 54,285 Views

A Crookes tube is an early experimental electrical discharge tube, with vacuum, invented by English physicist William Crookes   and others around 1869-1875, in which cathode rays , streams of electrons , were discovered.

Developed from the earlier Geissler tube, the Crookes tube consists of a partially evacuated glass bulb of various shapes, with two metal electrodes, the cathode and the anode , one at either end. When a high voltage is applied between the electrodes, cathode rays (electrons) are projected in straight lines from the cathode. It was used by Crookes, Johann Hittorf, Julius Plücker, Eugen Goldstein, Heinrich Hertz, Philipp Lenard and others to discover the properties of cathode rays, culminating in J.J. Thomson’s 1897 identification of cathode rays as negatively charged particles, which were later named electrons . Crookes tubes are now used only for demonstrating cathode rays.

Wilhelm Röntgen discovered X-rays using the Crookes tube in 1895. The term Crookes tube is also used for the first generation, cold cathode X-ray tubes, which evolved from the experimental Crookes tubes and were used until about 1920.

The picture below illustrates the operation of a Crookes tube in a schematic way.

For experiments with cathode ray tube we used an educational model readily available on eBay. It is a tube equipped with cathode and anode, with a mask with a slit so as to produce a planar cathode ray beam, there is also a fluorescent screen so as to highlight in a visual manner the presence of the beam. Two plates, used to demonstrate the influence of an electric field on the electron beam, complete the fixture. The images below show the apparatus.

The high voltage between anode and cathode is obtained with a HV generator powered with a 12 V, it generates a voltage value of 10 KV. The high voltage generator is a compact module easily available online, however you can use any HV generator, such as the ones based on diodes and capacitors in Cockcroft-Walton voltage multiplier configuration.

Magnetic Deflection

As we know, cathode rays are made up of electrons that are accelerated from the cathode to the anode. These are therefore negatively charged moving particles in a straight line, as such they are subject to the Lorentz force , which governs the motion of charged particles within magnetic fields. Generally speaking, the force exerted on a  charge  q  moving with speed v   within a  magnetic field B  and  electric field E , is calculated with the following formula :

In our case, the electric field is null and the moving charged particles are electrons, so the formula becomes:

F = – e (v x B)

Given the vector product between  v  and  B , the force is perpendicular to both the direction of the magnetic field and the velocity direction. The picture below illustrates the effect of Lorentz interaction.

This phenomena can be easily verified by using our cathode tube and a permanent neodymium magnet: by approaching the magnet to the tube, the beam is deflected low or upward depending on the polarity of the magnet. The image and video below show this experimental test.

Electric Deflection

The cathode ray beam is obviously sensitive to electric fields as well. From the law of Lorentz we get:

F = – e E

The force is proportional to the intensity of the electric field, and is directed in the opposite direction since the charge of the electron is negative, as shown in the picture below.

This experimental test can also be easily carried out with our cathode tube, as it is provided with a pair of deflection plates positioned close to the beam. By applying a voltage between 500 and 800 V, a clear deflection of the beam may be obtained. The image and video below show this experimental test.

https://youtu.be//QpcbeExV1LA?rel=0

If you liked this post you can share it on the “social” Facebook , Twitter or LinkedIn with the buttons below. This way you can help us! Thank you !

If you like this site and if you want to contribute to the development of the activities you can make a donation, thank you !

Tags Cathode Ray Tube

Gamma Spectroscopy with KC761B

Abstract: in this article, we continue the presentation of the new KC761B device. In the previous post, we described the apparatus in general terms. Now we mainly focus on the gamma spectrometer functionality.

Stack Exchange Network

Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

How did J. J. Thomson prove that the cathode rays were made of negative particles and not negative rays?

In Thomson's experiment, he used a discharge tube to prove that the cathode rays that emanate from the cathode were made of "a stream of negatively charged particles" because they were repelled by an applied negatively charged electrical field. Why did Thomson conclude from this experiment that the negatively-charged cathode rays were made of particles , and hence the discovery of the electron? Why did this force him to conclude that the rays were really particles? What am I missing here?

• history-of-chemistry

• 2 $\begingroup$ You are pursuing a distinction which is not there. $\endgroup$ –  Ivan Neretin Commented Dec 11, 2018 at 6:27
• 1 $\begingroup$ Check for wave–particle duality :) $\endgroup$ –  Kelly Shepphard Commented Dec 11, 2018 at 9:20
• $\begingroup$ I apologize. What I am asking is that I understand how Thomson discovered that the rays were NEGATIVE, but how did the experiment prove that the rays were made of PARTICLES? ( wave-particle duality was not discovered yet.....) $\endgroup$ –  suse Commented Dec 12, 2018 at 3:53
• 1 $\begingroup$ @IvanNeretin Wave particle duality does not imply what you think here unless nothing in the entire universe can ever meaningfully be described as a "particle". Electrons in cathode ray tubes behave far more like particles than waves and the relevant experiment was a major breakthrough in our understanding of matter well before quantum stuff became important. $\endgroup$ –  matt_black Commented Dec 13, 2018 at 14:05
• 2 $\begingroup$ The take home message is that a particle-stream is a ray. For example, how do you distinguish between a light ray and a stream of photons? $\endgroup$ –  Zhe Commented Dec 13, 2018 at 14:13

Thompson was able to measure the ratio of their mass to their speed

Cathode "rays" had been known for some time before Thomson. They were first observed as experiments in gas discharge tubes started to exploit better and better vacuums (the early experiments observed the varying forms of discharge in low pressure gases; cathode rays only become significant when there is very little gas left in the tubes).

At very high vacuums, people observed that the glass at the end of the tubes would glow even though the contents of the tubes did not (as there were too few gas particles left to cause a discharge). So the idea that some sort of ray was emitted by the cathode in the tube was developed. Initially the rays were seen to travel in straight lines.

Later, scientists such as Crookes observed that the rays could be deflected by magnetic fields (though he thought they were just negatively charged gas particles). Hertz, though, claimed electric fields would not deflect them (he was wrong).

The critical experiments done by Thompson relied on having an excellent glassblower who was able to construct an apparatus where electrodes inside the discharge tube which could be charged with an electric field (while retaining a very high vacuum). This enabled Thompson to refute the claim by Hertz that electric fields didn't cause deflection (maybe Hertz's glassblower wasn't as good). Once he had this apparatus further experiments with electric and magnetic fields could reveal a great deal more about the particles.

Thompson describes the critical experiments like this:

As the cathode rays carry a charge of negative electricity, they are deflected by an electrostatic force as if they were negatively electrified, and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter. The question next arises, What are these particles? Are they atoms, or molecules, or matter in a still finer state of subdivision? To throw some light on this point, I have made a series of measurements of the ratio of the mass of these particles to the charge carried by it (“Cathode rays,” Philosophical magazine, 44 (1897), 293-316, pdf of original available here )

[A good review and description of modern recreations of this experiment is given here]

The point of the experiments is that the deflection of the particle in a uniform electric field depends on its mass, velocity and charge. And its speed can be measured by carefully balancing the electric and magnetic fields to give zero net deflection (why this is so involves equations, but this is Chemistry.SE not Math.SE and you can read them in the paper).

So Thompson observed that cathode rays were best explained by a charged particle (a classical wave would not have been deflected) with an observable charge to mass ratio (which implied either a very large charge or a very small mass). And he observed that the particles were always the same regardless of the cathode material or the original gas in the tube.

Later experiments clarified the mass and charge. Which correspond to what we now call electrons.

Note that this happened well before any of the ideas of quantum mechanics and wave/particle duality appeared. Thompson was concluding, in contradiction to some theorists at the time, that the properties of cathode rays were better explained by particles obeying the known laws for electricity and magnetism than by a wave. And he was right. His discovery was the first time a key component of the atom had been identified.

• 1 $\begingroup$ Good answer. Do you it's helpful to explicitly say here that classical electromagnetic waves are not affected by electric/magnetic fields? $\endgroup$ –  Zhe Commented Dec 13, 2018 at 20:07
• 1 $\begingroup$ @Zhe good point. That was why Thompson was convinced it was particles not waves. $\endgroup$ –  matt_black Commented Dec 13, 2018 at 21:11

Your Answer

Reminder: Answers generated by artificial intelligence tools are not allowed on Chemistry Stack Exchange. Learn more

Sign up or log in

Post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Not the answer you're looking for? Browse other questions tagged electrons history-of-chemistry or ask your own question .

• Featured on Meta
• Preventing unauthorized automated access to the network
• User activation: Learnings and opportunities
• Join Stack Overflow’s CEO and me for the first Stack IRL Community Event in...

Hot Network Questions

• Including specific points in Plot
• Do we have volitional control over our level of skepticism?
• Do early termination fees hold up in court?
• How should I ask permission for using tables or figures from published papers, in my own paper?
• Matter made of neutral charges does not radiate?
• Sticky goo making it hard to open and close the main 200amp breaker
• Why do evacuations result in so many injuries?
• Purpose of sleeve on sledge hammer handle
• Is there a name for this Fibonacci formula that uses hyperbolic trigonometry?
• Literature reference for variance of the variance of the binomial proportion
• Undamaged tire repeatedly deflating
• All combinations of ascending/descending digits
• Problems regressing y on x/y?
• Why is my Lenovo ThinkPad running Ubuntu using the e1000e Ethernet driver?
• How similar were the MC6800 and MOS 6502?
• On a glassed landmass, how long would it take for plants to grow?
• Print 4 billion if statements
• Has Azerbaijan signed a contract to purchase JF-17s from Pakistan?
• How to do automated content publishing from CLI in XMCloud
• Why was Z moved to the end of the alphabet when Zeta was near the beginning?
• How to fix bottom of stainless steel pot that has been separated from its main body?
• Are there individual protons and neutrons in a nucleus?
• What happened with the 31.5 ft giant in Jubbulpore district (now Jabalpur), India, August 8, 1934?
• How do I avoid getting depressed after receiving edits?

• Study Abroad Get upto 50% discount on Visa Fees
• Top Universities & Colleges
• Abroad Exams
• Top Courses
• Read College Reviews
• Admission Alerts 2024
• Education Loan
• Institute (Counselling, Coaching and More)
• Ask a Question
• College Predictor
• Test Series
• Practice Questions
• Course Finder
• Scholarship
• All Courses
• B.Sc (Nursing)

Cathode Ray Experiment

Arpita Srivastava

Content Writer

The cathode ray tube is a type of vacuum tube where an electron gun will emit electron beams, which will display images on a phosphorescent screen. It helps in converting an electrical signal into a visual display.

• Cathode ray experiments can easily produce electrons which move from one atom to another in the form of electric current .
• The electrons are accelerated from one end of the tube to another with the help of an electric field.
• When the electrons hit the farthest end of the tube, they discharge all the energy they carry due to their speed.
• A small quantity of energy is transformed into X-rays .
• It is most commonly used in our television set in the form of a picture tube.

Key Terms: Cathode Ray Experiment, Cathode Ray Tube, Electrical Signal, Electron, X-rays, Atoms, Heat, Energy, Electric current, Electric Field, Magnetic Field

What is Cathode Ray Tube?

[Click Here for Sample Questions]

Cathode Ray Tube is a vacuum tube where an electron beam, deflected by applied magnetic or electric fields, creates a trace on a fluorescent screen. It was invented in 1897 by the German physicist Karl Ferdinand Braun.

• It is a vacuum glass envelope containing an electron gun, a source of electrons and a fluorescent light.
• The tube will accelerate and redirect the electrons with the help of internal or external means.
• Light is created when electrons hit a fluorescent tube.
• The front area of the cathode ray tube is scanned repeatedly to generate a fixed pattern called a  raster.
• These tubes are used in memory devices and computer monitors. 
• Speed of cathode rays is comparatively slower than light.

J. J. Thomson Experiment – The Discovery of Electron

The cathode ray experiment was first conducted in 1878 by an English physicist, William Crookes. Later in the 19th century, J. J. Thomson studied the characteristics and the constituents of cathode rays.

• The cathode rays were deflected by electrical and magnetic fields. 
• This behaviour was similar to that of a negatively charged particle, which suggested that the rays contained electrons.
• A discharge tube, also called a 'Crookes tube,' is made up of glass with two metallic plates. 
• One end is connected to the positive terminal, and the other to the negative terminal of the high-voltage power supply. 
• The plate connected to the negative terminal is the cathode, and the plate connected to the positive terminal is the anode.
• An electrical current was passed in the discharge tube experiment at a high voltage with low pressure. 
• Due to this current, a stream of rays spreading from the cathode passed through the tube. 
• These rays were named as the cathode rays.

Apparatus Setup 

JJ Thomson started the work on the cathode ray experiment in the late 1800s. A cathode ray discharge tube is a cylindrical glass tube that consists of two metallic electrodes, namely an anode and a cathode.

• The electrodes are connected to a battery that will accelerate the electrons.
• The gas released in the tube is kept at a pressure of 0.0001 atm.
• The pressure inside the tube is maintained by a vacuum pump. 
• Cathode rays will move from cathode to anode in a straight line in the absence of an electric and magnetic field.
• It will get deflected when placed in a magnetic and electric field.

Cathode Ray Discharge Tube 

Procedure of the Experiment

The procedure of the experiment is as follows:

• The equipment is set up by passing a high source voltage of 10,000 volts.
• This, in return, will set up a low pressure inside the cathode ray discharge tubes.
• The tubes are converted into conductors of electricity by passing voltage through metallic electrodes.
• For the identification of rays, an additional dipole was set up inside the apparatus.
• This will result in the deflection of rays from the negative terminal to the positive terminal.
• The process was continued by placing the phosphorescent substance and producing the fluorescent display on the screen.

After completing the experiment, J.J. Thomson concluded that rays are negatively charged particles present or moving around in a set of positive charges. 

• This theory helped physicists further to understand the atomic structure.
• The significant observation that he made was that the characteristics of cathode rays did not depend on the material of the electrodes.
• It is independent of the nature of the gas present in the cathode ray tube. 
• In a nutshell, we came to know that electrons are the basic constituents of all atoms.

The number of electrons dispersed outside the nucleus is equal to the number of positively charged protons present in the nucleus. This also explains the electrically neutral nature of an atom.

Uses of Cathode Ray Tube

The uses of cathode ray tubes are as follows:

• Cathode ray tubes are used in computer monitors used to use CRT technology.
• X-rays are produced with the help of this tube.
• The technology is used in the screen of a cathode ray oscilloscope, which is coated with fluorescent substances. 
• It is used in a video frame on an analogue television set.

Things to Remember

• A cathode ray tube is a vacuum tube which creates a trace on a fluorescent screen due to the presence of electric and magnetic fields.
• They are named after these rays are emitted by the negative electrode.
• Light is produced when electrons hit a fluorescent tube.
• Each cathode ray has similar properties irrespective of the elements.
• It is commercially used in CRT TV production.

Sample Questions

Ques. What are cathode ray tubes made of? (1 mark)

Ans. The cathode is made of a cesium alloy. Cesium is used as a cathode because it releases electrons readily when heated or hit by light.

Ques. Where can you find a cathode ray tube? (2 marks)

Ans. Cathode rays are electron streams observed in vacuum tubes (also known as an electron beam or an e-beam). If an evacuated tube of glass is fitted with two electrodes and a voltage is added, it is found that the glass opposite to the negative electrode glows from the electrons emitted by the cathode.

Ques. How did JJ Thomson find the electron? (2 marks)

Ans. In the year 1897 J.J. Thomson invented the electron by playing with a tube that was Crookes, or cathode ray. He proved that the cathode rays were charged negatively. Thomson understood that the accepted model of an atom did not account for the particles charged positively or negatively.

Ques. What are the properties of cathode rays? (3 marks)

Ans. The properties of cathode rays are as follows:

• Cathode rays move in a straight line and are able to cast sharp shadows.
• Magnetic field and electric field deflect these rays.
• They are produced at the cathode (negatively charged electrode) and travel towards the anode (positively charged electrode) in a vacuum tube.
• The properties of the cathode rays do not depend on the electrodes and the gas used in the vacuum tube.
• Speed of these rays is comparatively slower than light.
• They can penetrate through thin metal plates.
• Phosphors glow if cathode rays fall on it.

Ques. What do you mean by cathode? (2 marks)

Ans. A device’s anode is that terminal through which current flows in from outside. A device’s cathode is its terminal through which current flows out. Electrons are charged negatively, positive current flowing in is the same as out flowing electrons.

Ques. Who discovered the cathode rays? (2 marks)

Ans. In the year 1858, Plücker discovered cathode rays by sealing a couple of electrodes inside the tube, evacuating the air and forcing it between the electric current of the electrode. Cathode rays are negatively charged. They are 180 o  times lighter than hydrogen, the lightest element.

Ques. What is the Colour of cathode rays? (2 marks)

Ans. Cathode-ray tube (CRT), vacuum tube which produces images when electron beams strike its phosphorescent surface. CRTs can be coloured (using usually three electron guns to produce red, green, and blue images that render a multicoloured image when combined) or monochrome (using one electron gun).

Ques. How are cathode rays formed? (2 marks)

Ans. Cathode rays come from the cathode, as the cathode is negatively charged. The rays strike and ionize the gas sample inside the container. The electrons ejected from gas ionization travel to the anode. These rays are electrons that are actually created from the gas ionization inside the tube.

Ques. What are the components used in the cathode ray discharge tube? (4 marks)

Ans. The components used in the cathode ray discharge tube are as follows:

• A focused electron beam is produced by the electron gun or heater.
• Electrons are accelerated by anodes.
• The direction of the electron beam can be continually changed because to the extremely low-frequency electromagnetic field produced by deflecting coils.
• There are two varieties of deflecting coils: vertical and horizontal.
• It is possible to change the beam's intensity.
• A tiny, brilliant visible spot appears on the fluorescent screen as the electron beam strikes the phosphor-coated screen.

Ques. What are the observations of cathode ray experiment? (3 marks)

Ans. The observations of cathode ray experiment are as follows:

• Cathode rays moves from cathode terminal to anode terminal of the battery.
• It travel in a straight line in absence of electric and magnetic field but get deflected in presence of these fields.
• The rays are observed with the help of fluorescent screens.
• The direction of negative rays indicate that these rays are negatively charged.

Ques. What was the result of the cathode ray discharge tube exper­iment? (3 marks)

Ans. The result of the cathode ray discharge tube exper­iment are as follows:

The type of gas in the tube has no bearing on the mass and charge of cathode rays. Electrons are negatively charged particles found in cathode rays. It was determined that every atom had electrons since every gas emits cathode rays.

For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates

Check-Out: 

CBSE CLASS XII Related Questions

1. using the standard electrode potentials given in table 3.1, predict if the reaction between the following is feasible:  (i) fe 3+ (aq) and i - (aq)  (ii) ag + (aq) and cu(s)  (iii) fe 3+ (aq) and br - (aq)  (iv) ag(s) and fe 3+ (aq)  (v) br 2 (aq) and fe 2+ (aq)., 2. discuss briefly giving an example in each case the role of coordination compounds in: biological systems medicinal chemistry analytical chemistry extraction/ metallurgy of metals, 3. which of the following compounds would undergo aldol condensation, which the cannizzaro reaction and which neither write the structures of the expected products of aldol condensation and cannizzaro reaction.  \((i) methanal \) \((ii) 2-methylpentanal \) \((iii) benzaldehyde \) \((iv) benzophenone \) \((v) cyclohexanone \) \((vi) 1-phenylpropanone \) \((vii) phenylacetaldehyde \) \((viii) butan-1-ol \) \((ix) 2, 2-dimethylbutanal\), 4. depict the galvanic cell in which the reaction zn(s) + 2ag + (aq) → zn 2+ (aq) + 2ag(s) takes place. further show:   (i) which of the electrode is negatively charged   (ii) the carriers of the current in the cell.   (iii) individual reaction at each electrode., 5. in the button cells widely used in watches and other devices the following reaction takes place: zn(s) + ag 2 o(s) + h 2 o(l)  \(\rightarrow\)  zn 2+ (aq) + 2ag(s) + 2oh -  (aq)  determine  \(\triangle _rg^\ominus\)  and  \(e^\ominus\)  for the reaction., 6. write down the electronic configuration of: (i) cr 3+ (iii) cu + (v) co 2+ (vii) mn 2+   (ii) pm 3+ (iv) ce 4+ (vi) lu 2+ (viii) th 4+, subscribe to our news letter.

Talk to our experts

1800-120-456-456

• Cathode Ray Experiment

What are Cathode Rays?

Cathode rays are a beam of negatively charged electrons traveling from the negative end of an electrode to the positive end within a vacuum, across a potential difference between the electrodes.

How Do the Cathode Rays Work?

The cathode is a negative electrode, Anode is the positive electrode. Since electrons are repelled by the negative electrode, the cathode is the source of cathode rays inside a vacuum environment. When a potential difference is applied, the electrons jump to an excited state and travel at high speeds to jump back-and-forth inside the vacuum glass chamber and when some cathode rays certain molecules of the cathode screen, they emit light energy. A wire is connected from anode to cathode to complete the electrical circuit.

Construction of a Cathode Ray Tube

Its Basic Components are: -

Electron Gun Assembly: - It is the source of the electron beams. The electron gun has a heater, cathode, pre-accelerating anode, focusing anode and accelerating anode.

Deflecting Plates: - They produce a uniform electrostatic field only in one direction, and accelerate particles in only one direction.

Screen: - The inner layer of the screen is coated with phosphorus, and produces fluorescence when cathode rays hit the screen by a process of phosphorus excitation.

Aquadag: - It is an aqueous solution of graphite used to collect the secondary emitted electrons which are required to keep the cathode ray in electrical equilibrium.

What is the Cathode Ray Tube Experiment?

In 1897, great physician J.J. Thompson, conducted his first cathode ray tube experiment to prove that rays emitted from an electron gun are inseparable from the latent charge. He built his cathode ray tube with a metal cylinder on the other end. The metal had two small diversions(slits), leading to an electrometer that could measure a small electric charge. From the first experiment, he discovered that the electrometers stopped measuring electric charge. From this, he deduced that the electric charge and the cathode rays must be combined and are the same entity.

Then he conducted a Second experiment, to prove the charge carried by the cathode rays was negative or positive. Now, he put a negatively charged metal plate on one side of the cathode rays to go past the anode, and a positively charged metal plate on the other side. Instead of an electrometer at one end of the Cathode Ray Tube, he used a fluorescent coated tube that would glow where the cathode ray hit it. When the charged metal plates were introduced he found that the cathode rays bent away from the negative plate and towards the positive plate. This proved that the cathode rays were negatively charged.

Then he performed the third experiment, to know the nature of the particles and reduce the mass of the particles as they had too small of a mass to be calculated directly. For the experiment, he used the cathode ray tube and with a high applied potential difference between the two electrodes, with the negatively charged cathode producing the cathode rays. He had already deduced that the particles were negatively charged. Firstly, he applied an electric field in the path between anode and cathode and measured the deflections from the straight path. Now he applied a magnetic field across the cathode ray tube by using an external magnetic field. The cathode ray is deflected by the magnetic field. Now he changed the direction of the external magnetic field and found that the beam of electrons is deflected in the opposite direction. From this experiment, he concluded that the electrostatic deflection is the same as the electromagnetic deflection for the cathode rays and he was able to calculate the charge to mass ratio of the electron.

After these three experiments, he deduced that inside the atom there consist of a subatomic particle, originally named ‘corpuscle’, then changed to ‘electron’ which is 1800 times lighter than the mass of hydrogen atom (Lightest atom).

Formula Used

The derivation of the formula used to calculate the charge to the mass ratio:

For Electric Field the force on a particle is

Force(F)=Charge(Q)*Electric field(E) ---<1>

For Magnetic Field the force on a particle moving with velocity is:

F=q*velocity(v)*Magnetic Field(B) ---<2>

From 1 and 2 we get,

V=E/B ----<3>

From the definition of Force,

Acceleration(a)= Force(f)/mass(m) ----<4>

Combining 1 and 4

a=q*E/m ----<5>

From Newton’s law Of motion, vertical displacement is:

Y= (1/2)*a*t*t ----<6>

From 5 and 6

q/m=(2*y*v*v)/x*x*E

Cathode Ray Tubes (CRT) 

The cathode ray tube (CRT) is a vacuum tube, in which electrons are discharged from the cathode and accelerated through a voltage, and thereby gains acceleration of some 600 km/s for every volt. These accelerated electrons collide into the gas inside the tube, thereby allowing it to glow. This enables us to see the path of the beam. Helmholtz coil, a device for producing a region of nearly uniform magnetic field, is also used to apply a quantifiable magnetic field by passing a current through them.

A magnetic field will cause a force to act on the electrons which are perpendicular to both the magnetic field and their direction of travel. Thus, a circular path will be followed by a charged particle in a magnetic field. The faster the speed of a charged particle in a magnetic field, the larger the circle traced out in a magnetic field. Contrarily, the larger the magnetic field needed for a given radius of curvature of the beam. The paths of the electrons are distorted by the magnet in CRT Tv when they are brought near the screen. The picture on the screen appears when the electrons accurately hit phosphors on the back of the screen. Because of this, different colors of light are emitted on the screen when the electrons are impacted. Hence, the electrons are forced to settle in the wrong place, thereby causing the distortion of the image and the psychedelic colors.

Postulates of J.J. Thomson’s Atomic Model

After the Cathode ray tube experiment, Thomson gave one of the first atomic models including the newly discovered particle. 

His model stated: -

An atom resembles a sphere of positive charge with a negative charge present inside the sphere.

The positive charge and the negative charge were equal in magnitude and thus the atom had no charge as a whole and is electrically neutral.

His model resembles a plum pudding or watermelon. It assumed that positive and negative charge inside an atom is randomly spread across the whole sphere like the red part of the watermelon (positive charge) and the black seeds (negative charge).

Practical Uses of Cathode Ray Tube Experiment

In ancient times, the cathode ray tubes were used in the beam where the electron was considered with no inertia but have higher frequencies and can be made visible for a short time.

Many scientists were trying to get the secrets of cathode rays, while others were in search of the practical uses or applications of cathode ray tube experiments. And the first search was ended and released in 1897 which was introduced as Karl Ferdinand Braun’s oscilloscope. It was used for producing luminescence on a chemical affected screen in which cathode rays were allowed to pass through the narrow aperture by focusing into the beams that looked like a dot. This dot was passed for scanning across the screen which was represented visually by the electrical pulse generator. 

Then during the first two to three decades of the twentieth century, inventors continued to search the uses of cathode ray tube technology. Then inspired by Braun's oscilloscope, A. A. Campbell advised that a cathode ray tube would be used for projecting video images on the screen. But, this technology of the time did not get matched with the vision of Campbell-Swinton. It was only until 1922, when Philo T. Farnsworth developed a magnet to get focused on the stream of electrons on the screen, for producing the image. Thus, the first kind of it, Farnsworth, was quickly backed up by Zworykin’s kinescope, known as the ancestor of modern TV sets.

Nowadays, most image viewer devices are made with the help of cathode ray tube technology including the guns of electrons which are used in huge areas of science as well as medical applications. One such use for cathode-ray tube research is the microscope invented by Ernst Ruska in 1928. The microscope based on electrons uses the stream of electrons to magnify the image as the electrons have a small wavelength which is used for magnifying the objects which are very small to get resolved by visible light. Just like Plucker and Crookes work, Ernst Ruska used a strong field of magnetic lines for getting it focused on the stream of electrons into an image.

Solved Example:  

Question: The charge of an electron e=1.602∗10−19 and its is mass m=9.11∗10−31. The stopping potential of an electron traveling in a cathode ray tube is V=5V. Find the velocity of an electron traveling (where charge of an electron e=1.602∗10−19 and mass m=9.11810−31).

Answer: Here we need to find the velocity of traveling electrons using the given stopping potential.

We know that eV=12mv2, the charge(e) and mass(m) of the electron is also given as,

e=1.602∗10−19 and m=9.11∗10−31

By substituting the values of e, m, V.(1.602∗10−19)(5)

=12(9.11∗10−31)(v2)v2

=(1.602∗10−19)(5)(2)9.11∗10−31v

=1.33∗106m/s             

FAQs on Cathode Ray Experiment

1. What is the procedure of the Cathode Ray Experiment?

The apparatus of Cathode Ray Experiment is arranged in such a way that the terminals have high voltage with the internal pressure, which is reduced by removing the air inside the CRT. Because of the high voltage in the terminal,  the partial air inside it is ionized and hence gas becomes the conductor. The electric current propagates as a closed-loop circuit. In order to recognize and measure the ray produced, a dipole is set up. The cathode rays will begin deflecting and repel from the dipole and move towards the anode because of the dipole. The phosphorescent substance is arranged in such a way that the rays strike the substance. And hence, it causes small sparks of light, which detects the stream of rays.

2. What are Cathode ray tubes?

Cathode ray tubes (CRT) are a presentation screen that produces pictures as a video signal. Cathode ray tubes (CRT) is a type of vacuum tube that displays pictures when electron beams from an electron gun hit a luminous surface. The CRT produces electron beams, accelerates them at high speed, and thereby deflecting them to take pictures on a phosphor screen. Electronic presentation gadgets being the most established and least expensive electronic presentation innovation, were initially made with CRTs. CRTs work at any aspect ratio, at any resolution, and geometry without the need to resize the picture. CRTs work on the principle of an optical and electromagnetic phenomenon, called cathodoluminescence.

3. What are the applications of Cathode ray tubes?

The following are the applications of Cathode ray tubes.

The main components of a cathode ray tube (CRT) includes A Vacuum tube holding an electron cannon and a screen lined with phosphors.

The technology of Cathode ray tubes is used by Televisions and computer monitors. Three electron cannons correlate to corresponding types of phosphors in color CRTs, one for each main color viz red, green, and blue.

Ancient computer terminals and black and white televisions are examples of monochromatic CRTs.

cathode ray tube (CRT) is also used in oscilloscopes, which are machines that display and analyze the waveform of electronic signals.

A cathode ray amusement device was the very first video game to be produced, which were used in old military radar screens.

4. What are the basic principles of the CRT?

There are three basic principles of the CRT as the following:

Electrons are released into a vacuum tube from very hot metal plates.

The released electrons are accelerated and their direction of movement is controlled by using either a magnetic field from a coil that is carrying an electric current or by a voltage between metal plates.

A high-velocity beam of electrons hits some materials such as zinc sulfide. The spot is created on the fluorescent screen, and it causes material, called a phosphor, to glow, giving a spot of light as wide as the beam.

5.  How to understand the concept of the Cathode Ray Experiment easily?

Students can understand the concept of the Cathode Ray Experiment easily with the help of a detailed explanation of the Cathode Ray Experiment provided on Vedantu. Vedantu has provided here a thorough explanation of the Cathode Ray Experiment along with Cathode Rays, How Do the Cathode Rays Work, Construction of a Cathode Ray Tube, Postulates of J.J. Thomson’s Atomic Model, and Practical Uses of Cathode Ray Tube Experiment along with examples. Students can learn the concepts of all the important topics of Science subject on Vedantu.

NCERT Study Material

• Chemistry Class 9 Notes
• Physical Chemistry
• Organic Chemistry
• Inorganic Chemistry
• Analytical Chemistry
• Biochemistry
• Chemical Elements
• Chemical Compounds
• Chemical Formula
• Real life Application of Chemistry
• Chemistry Class 8 Notes
• Chemistry Class 10 Notes
• Chemistry Class 11 Notes
• Chemistry Class 12 Notes

Cathode Ray Experiment

Cathode Ray Experiment , also known as the Crookes tube experiment , is a historically significant experiment in the field of physics that helped scientists understand the nature of electrons. English scientist Sir J.J. Thomson performed an experiment using a Cathode Ray Tube, which led to the discovery of an electron.

In this article, we will discuss this significant experiment, including details of the Cathode Ray Tube, the procedure of the experiment, and J.J. Thomson’s observations, which led to one of the greatest discoveries in the field of science.

Table of Content

• What is the Cathode Ray Experiment?

What is Cathode Ray Tube (CRT)?

• Experiment Setup

Applications of Cathode Ray Experiment

• Limitations of the Cathode Ray Experiment

What is Cathode Ray Experiment?

Cathode Ray Experiment, also known as the Cathode Ray Tube (CRT) Experiment, is a fundamental experiment in the history of physics that played a crucial role in understanding the nature of electrons and contributed to the development of modern electronics and television technology.

The experiment was first conducted by Sir William Crookes in the 1870s and later improved upon by scientists like J.J. Thomson in the late 19 th and early 20 th centuries.

Who is J.J. Thomson?

Joseph John Thomson, often called J.J. Thomson, was a British physicist celebrated for winning the Nobel Prize in Physics in 1906 for his research on how electricity moves through gases. His notable achievement was the discovery of the electron during the Cathode Ray Experiment.

A Cathode Ray Tube (CRT) is a special glass tube that played a big part in J.J. Thomson’s important experiment. This clever device helped scientists understand tiny particles that make up atoms.

Structure of CRT

CRT has a simple structure. It’s a sealed glass tube with two electrodes at each end – one is called the cathode (negative), and the other is the anode (positive). When these electrodes are connected to power, they create an electric field inside the tube. The tube is made empty, like a vacuum, so there’s no air inside.

The vacuum is essential because it lets cathode rays move in a straight line from the cathode to the anode without any interference from air. This controlled setup helps scientists study the behavior of cathode rays in different situations. The CRT is a key tool that led to important discoveries about the tiniest building blocks of matter.

Cathode Ray Experiment Setup

Below is the detailed setup for the Cathode Ray Tube Experiment with the elements used along with the diagram:

• Cathode Ray Tube (CRT): A sealed glass tube with a cathode and anode at either end.
• Cathode: A negatively charged electrode inside the CRT.
• Anode: A positively charged electrode inside the CRT.
• High Voltage Generator: A power supply capable of providing a high voltage between the cathode and anode.
• Vacuum Pump: A pump to evacuate air from the CRT to create a low-pressure environment.
• Discharge Tube: The entire CRT assembly including the cathode, anode, and vacuum space.
• Perforated Anode Disk: Placed at the anode end to allow some cathode rays to pass through.

Procedure of Experiment

Below is the procedure steps for the experiment with the perspective of the JJ Thomson:

• JJ Thomson created a sealed cathode ray tube with minimal air inside.
• Connected the tube to a power source, causing electrons (cathode rays) to shoot out.
• Observed electrons moving in straight lines inside the vacuum of the tube.
• Introduced an electric field by adjusting the power, causing electrons to change their path.
• Experimented with magnets, observing electrons being affected and swerving in response.
• Adjusted power settings to observe changes in electron movement, establishing consistent patterns.
• Systematically recorded electron behavior in various situations.
• Determined the charge-to-size ratio of electrons, making a significant discovery.
• Concluded that cathode rays were composed of tiny particles known as electrons.
• Thomson’s discovery revolutionized understanding of the microscopic world’s building blocks.

Observation of Cathode Ray Experiment

In the Cathode Ray Experiment, J.J. Thomson made a ground breaking observation i.e., when cathode rays encountered electric and magnetic fields, they exhibited intriguing behavior. Thomson noticed their deflection, and the direction of this deflection pointed to a negative charge. This pivotal observation led Thomson to the groundbreaking conclusion that cathode rays were composed of negatively charged particles, now recognized as electrons.

Conclusion of Cathode Ray Experiment

Cathode Ray Experiment marked a revolutionary moment in the realm of science. J.J. Thomson’s demonstration of cathode ray deflection and the identification of these rays as negatively charged particles conclusively affirmed the existence of subatomic particles. This groundbreaking experiment transformed our comprehension of atomic structure, shattering the notion that atoms were indivisible. Instead, Thomson’s work revealed the presence of smaller components within atoms. This pivotal episode in the history of physics not only altered fundamental perspectives but also laid the foundation for subsequent advancements in the field.

The Cathode Ray Experiment, conducted by Sir J.J. Thomson in 1897, led to several significant applications and advancements in various fields:

• Discovery of the Electron: The most direct outcome of the Cathode Ray Experiment was the discovery of the electron, a fundamental component of atoms. This discovery was pivotal in the development of atomic theory and quantum physics.
• Television and Computer Monitors: The technology behind cathode ray tubes (CRTs) was essential in the development of early television and computer monitors. These devices used electron beams, controlled and focused by magnetic or electric fields, to illuminate phosphors on the screen, creating images.
• Medical Imaging: Cathode ray technology found applications in medical imaging, particularly in early forms of X-ray machines and later in more advanced imaging technologies.
• Electron Microscopy: The principles discovered in the Cathode Ray Experiment were integral to the development of electron microscopy, which uses a beam of electrons to create an image of a specimen. This technology allows for much higher resolution than traditional light microscopy.

Limitations of Cathode Ray Experiment

The Cathode Ray Experiment, while groundbreaking in its time, had several limitations:

• Lack of Precise Measurement Tools: At the time of Thomson’s experiments, the precision and accuracy of measurement tools were limited. This meant that the measurements of the charge-to-mass ratio of electrons were not as accurate as what can be achieved with modern equipment.
• Incomplete Understanding of Subatomic Particles: Thomson’s experiment was conducted at a time when the structure of the atom was not fully understood. This meant that while the experiment led to the discovery of the electron, it did not provide a complete picture of subatomic particles and their interactions.
• Limited Control over Experimental Conditions: The vacuum technology and methods to control the electric and magnetic fields in Thomson’s time were rudimentary compared to today’s standards. This limited the ability to control experimental conditions precisely.
• Atomic Structure
• Discovery of Electrons

Cathode Ray Experiment – FAQs

J.J. Thomson, whose full name is Joseph John Thomson, was a British physicist born on December 18, 1856, in Cheetham Hill, Manchester, England, and he passed away on August 30, 1940. He is best known for his discovery of the electron, a fundamental subatomic particle.

What are Cathode Rays?

Cathode rays are streams of electrons observed in a vacuum when a high voltage is applied between electrodes in a cathode ray tube (CRT). These rays were first discovered and studied by J.J. Thomson in the late 19th century.

What was the Cathode Ray Experiment?

The cathode ray experiment, conducted by J.J. Thomson in the late 19th century, was a series of experiments that led to the discovery of electrons and provided crucial insights into the nature of subatomic particles.

What are Two Conclusions of the Cathode Ray Experiment?

Two conclusion of Cathode Ray Experiment are: Cathode rays are streams of negatively charged particles (electrons). These particles are fundamental components of all atoms.

Why did J.J. Thomson Experimented with Cathode?

J.J. Thomson experimented with cathode rays to investigate their nature and to understand the internal structure of atoms.

Similar Reads

• School Chemistry
• Geeks Premier League
• Geeks Premier League 2023
• Chemistry-Class-9
• Physical-Chemistry

Please Login to comment...

• Best Smartwatches in 2024: Top Picks for Every Need
• Top Budgeting Apps in 2024
• 10 Best Parental Control App in 2024
• Top Language Learning Apps in 2024
• GeeksforGeeks Practice - Leading Online Coding Platform

Improve your Coding Skills with Practice

What kind of Experience do you want to share?