Cathode Rays Lead to Thomson's Model of the Atom

In the mid 1800's scientists successfully passed an electric current through a vacuum in a glass tube. They saw a glow from the tube that seemed to emanate from the negatively charged plate called the cathode. Since scientists didn't know what the glow was they called it a cathode ray. There was debate over whether the cathode ray was a wave phenomenon like light or a stream of negatively charged particles. JJ Thomson effectively resolved the debate in 1897 by performing a clever experiment that determined the charge to mass ratio of the particles making up the cathode ray. He also showed that this same particle was in all different cathode materials so it must be a constituent common to all atoms. This changed our understanding of the atom from the previous billiard ball model to Thomson's plum pudding model of the atom.

[ToddHowardWithAGun]

"What's an electron?"
"Well, think of it as a plum pudding..."

[banhisikhadebnath]

9 yrs passed and this was the 1st video of yours that I saw

[ayushjaiswal.]

1:50 Derek listening like a serious student

[cabelodomato]

I am loving to watch your old YouTube videos. And do you know what?
I just thought that it may be possible to start to present those videos to my 8 years old girl. They are shorter and simpler to understand. Perfect for kids!

Thank you very much for making such nice videos over the years.

[pauleohl]

What we see here raises more questions than it answers. I was looking for a ray and I see rising doughnuts of purple light. Also, do the electrons that were pulled off the cathode return? If so, how and when do they return? If not, where do they go?

[douglasstrother]

"Electromagnetic Fields and Waves" by Lorrain & Corson (2nd Edition) contains a problem in chapter 2 "Electrostatic Fields in a Vacuum" (2-19) on J.J. Thomson's "Plum Pudding" model of the atom. It asks to (A) find the force on an electron; (B) describe its motion; (C) the frequency for a 1 Angstrom-sized atom; and (D) compare this frequency to that of visible light.

A rather thought-provoking question in an Undergraduate E&M textbook!

[crane]

How he says ‘laindmaak’ 00:16 (land mark) is the most Australian thing ever

[dougk]

1:50 distracted by the vac pump. It looks like a shark! Lol

[maxpercer]

i wish they would explain how the electron produces the light, like a schematic from the cathode to the anode

[bhatts]

Watching this 10 years after it was originally posted!

[ElVerdaderoAbejorro]

This raises so many questions:

1) If they were expecting to see "nothing or a spark", how come they saw they "saw the same glow no matter what metal they did the experiment"?
2) How on earth did they measure the size of this particle to conclude it is smaller than an atom?
3) When does this particle (electron) become a photon and how does that conversion work?

[InvertedWingback]

This guy might become a great channel a decade later

[JonandAlly]

P.s. Love your videos and don't think u try to make ppl look stupid (and never watched the full interviews)! And love the point about "unknowledgeable" vs. unintelligent.

[laimiskleinauskas]

it reminds me experiment of thermoemission in physics lab. like the force they were talking was a heat emitted because of R of the cathode.

[winneriruke]

This was helpful I wish I can study in your university

[wondroustransition]

What happens after you turn the power off though? ... I mean during the experiment all the electrons are "sucked out" of the cathode if I understood that right? What remains? Will the cathode be forever positively charged after we cut the power? Or how do the electrons get back to the cathode?
Where do the electrons go during the experiment? Will they just stick to the anode and remain there as long as there is power?

[mashburger]

your video is a life saver thanks very much. kinda got a write a paper on this tonight :/

[gabrielhacecosas]

Why can't you see a continuous "spark"? is not an effect of the camera, I've done that experiment with a flybak, a bottle of wine and a fridge pump and you can see the spark discontinuously. Is it because the high voltage is not continuous but pulsating?

[crkreads]

Experiment first conducted in 1857 ...wow some really intelligent people that time.

[eddieoneil]

Seeing young Veritasium is something veryy delightable