Rutherford Gold Foil Experiment – Backstage Science

Rutherford Gold Foil Experiment – Backstage Science


[Music] at the time he carried out the experiment Tom the Ottoman was thought to be a blob of positive charged with negative electrons embedded inside it now Rutherford set up an experiment to direct a beam of alpha particles which he knew to be heavy positively charged particles and we now know to be the nuclei of helium atoms through a very thin gold foil the brass can in the center of the picture contains a small americium-241 source producing alpha particles most of the particle is absorbed in the brass there is a small opening producing a beam of alpha particles they passed through gold foil which is about 1.5 microns in thickness and they are then detected by one of the two detectors set up behind the foil one of the detectors counts particles going straight ahead which is the majority and we count a rate of between one and two thousand per second the second counter we can move to measure the scattering rate as a function of angle now the experiment that he and his colleagues carried out was very laborious and involved them City four hours in a dark dark room holding a tiny fluorescent screen and looking just by eye for flashes of light on the screen we’ve replicated that with modern detectors technology in its current position behind the foil it will measure one count every few seconds [Music] as rather deduced most of the gold items empty space so the alpha-particle just go straight through doesn’t see anything and go through in a straight line occasionally one of the particles will come close enough to the nucleus of the gold item but it will be deflected by the electric field from positive nucleus if it comes at a glancing blow we deflected through a small anger you can hit it head on it’ll just bounce right back and it’s fascinating I think to do them that this was this was telling us something very important that we didn’t know about the very deep structure of matter it showed that the Assam had a heavy nucleus with mostly empty space with electrons distributed around it which is exactly the picture we now have it was also the start of particle physics what Rutherford was doing what we’re doing here is taking a beam of particles firing as a target looking at the way the particles are scattered and from that deducing what was going on inside the target and hundred years ahead we now have the large hadron collider where we do the same thing we fire a beam of particles at a target in that case the target is another beam coming the other way we look for the particles being scattered out of that collision process and tries to deduce what was going on in the collision from the behavior the scattered particles and all that comes from Rutherford’s original idea of firing a beam at a target so in a century we’ve come from an apparatus that would fit on the desk there was at the cutting edge of physics – the Large Hadron Collider which is 27 kilometers in circumference what was happening was the alpha particles were going through and missing the nucleus because the nucleus is extremely small on the estimate by comparison is very big so it’s almost all empty space and we have to wait a long time before one of those alpha particles hit the nucleus almost head-on and bounce back into our detector [Music]

100 Comments

  1. @nodariel
    Yes, and they did it by holding a phosphorescent screen behind the source of alpha particles and watched it closely in pitch dark… for hours at a time. Watch the BBC documentary series "Atom", its on the tube.

  2. This is the best explanation of the Rutherford Experiment I've ever watched. Very clear and it has a working replica of the experiment.

  3. @iiAngelic this is wat i understand alpha particles r positive so wen they come in contact with the proton very close they deflect back i'm i correct if u get the correct answer tell me pls

  4. @iiAngelic A negative and negative deflected like a magnet and how he found out I believe was by using a nucleus that was negatively charged so every time a electron would go thru it would bounce back in various directions

  5. why the doorbell sound it almost stoped me from watching this video, learn not to use such irritating sounds the next time DX

  6. By far the best explanation of Rutherford's Gold Foil Experiment and Plumb Pudding model that I"VE ever seen…

  7. wt abot the alpha particle vch mak head to head contact with the nucleus? that part is not mentiond here. any hv nyc n imformative

  8. Well but the electrons were not spread randomly, as what shrodinger said that the electrons are spread in organised clouds of electrons…

  9. Not hard to get. I'd probably cheat and plate some thin copper and then disolve the center 🙂 . Old electronics have a fair bit of gold plating ( early 70s it could be gold alloy ) and if you just need a strip then drop a wire wrap pin ( old style apx 1 mm by 2 mm ) into some dilute nitric and wait. If you find a Burrows B500 computer to strip, I'd like an invitation to your yacht afterwards 😀

  10. A lot of speaker wire and headphone jacks/plugs today use gold plating/wires as well since it causes the least amount of interference. You could probably get gold the same way from there as well ^.^

  11. It has nothing to do with interference. Copper and aluminum are more likely to oxidize than Gold. Interference is caused by inductance or magnetic fluctuations caused by alternating electrical current.

  12. They definitely repeat the experiment without the particle source, then subtract this control from the measured count. This matters only if you want to quantify the result, the phenomena is obvious without this control.

  13. if alpha particles are helium nuclei (lighter than air) surely it makes more sense to place the detector above the alpha decay outlet – also what about the atoms in the air causing interference!

  14. I put on video, walked away heard the bell ring, paused the video. checked who was at the door, walked back pressed play, heard it again paused. this happen one more time. reset, the video read what it said! and 🙂 lol

  15. Marvin Cervantes:"the brass can? does brass behave the same way that Lead did back in Rutherfords day?"

    Brass and pretty much most metal will work because it stops alpha particles. The gamma ray will mostly pass through and they will hit the detector head on. All you need to do is remove the gamma ray counts from the counter.

  16. Does that ringing bell tells us that alpha particle is detected by alpha detector..and yeah those detectors must be present @ angel of 180 Degree too.

  17. That's my father. He was a really intelligent guy and I am still so proud of him. <3
    I say 'was'…. he passed away from cancer in 2013.
    But it's nice knowing that if I want to hear his voice again all I have to do is watch this video.
    Thank you.

  18. The gold foil is 1.5 microns thick, and the gold atoms atoms are in the nanometer range… how many layers of gold atoms does the helium nuclei need to avoid to pass through without deflection? Thousands? ….Why is only one gold atom shown in the model? That doesnt look like an accurate model to me. How frequently are the alpha particles being emitted? Does gold foil that thick present an effectively solid wall of gold? If helium nuclei pass through easily, how about helium atoms? How about water? Wouldnt a pin-ball sort of behavior be expected for the alpha particles? Helium is a noble gas, but a helium with a +2 charge would be an incredibly reactive ion, desperately seeking electrons…could it react chemically?? These are the sorts of questions that anyone would wonder about. I do. 

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