Why the interference pattern looks like the diffraction made by a single small hole? Shouldn't the electron-wave be diffracted by all the atoms in the graphite? I would expect that by increasing the voltage to get an interference pattern close to the X-ray diffraction pattern in crystals...How is tat?
@freemanx2x In short, its because the material is polycrystalline. The target is a copper grid with graphite deposited on it, that graphite consists of an agglomeration of tiny crystalline graphite domains (hence polycrystalline). Each of these domains has an identical crystal structure, but they are randomly oriented with respect to one another.
A large number of these sit within the cross-sectional area of the incident electron beam. Some will have an orientation such that the incident...
@micolich ... such that the incident beam comes in at the Bragg angle, and this produces strong diffraction out to the first ring that you see. The second ring corresponds to the 2nd order situation for above. The domains where the electron beam doesn't come in at the Bragg angle destructively diffract, so these don't blur the signal.
If you then think through all the possible ways you can orient the diffracting domains so that Bragg's law holds (you might need to draw this up), you get a ring.
@micolich For more info, try looking up the 'powder crystalline diffraction method', I think it was developed by Debye and ummm, Scherrer (or maybe its von Laue). You are right though, if you had a pure single crystal in there, you'd get an x-ray like diffraction pattern. Try looking at wikipedia's electron diffraction page for an image of this (youTube won't let me post the link).
I have done this experiment in my Physics class a month ago and it is pretty cool but it also got me thinking and I know that I could be totally wrong but I have a few questions.
* Could the electron be radiating EM radiation that is causing the interference pattern?
* Has this experiment ever been done with neutrons?
* Does the 'matter wave' travel at the electron speed or the speed of light?
@adam3141 Q1: No, because the light is emitted when the electron reaches the phosphor, so it does map where the electron hits the screen. Q2: Yes, it has, it has even been done recently with C60 (buckyballs). Q3: The speed of travel is a difficult one, I need many more characters to answer. Q4: No, the electron did not undergo quantum teleportation.
What about the observation problem? Can observation alter these results ? to show either way ? Sometimes it wants to be particle some times it behaves like a wave?
Why the interference pattern looks like the diffraction made by a single small hole? Shouldn't the electron-wave be diffracted by all the atoms in the graphite? I would expect that by increasing the voltage to get an interference pattern close to the X-ray diffraction pattern in crystals...How is tat?
freemanx2x 1 month ago
@freemanx2x In short, its because the material is polycrystalline. The target is a copper grid with graphite deposited on it, that graphite consists of an agglomeration of tiny crystalline graphite domains (hence polycrystalline). Each of these domains has an identical crystal structure, but they are randomly oriented with respect to one another.
A large number of these sit within the cross-sectional area of the incident electron beam. Some will have an orientation such that the incident...
micolich 1 month ago
@micolich ... such that the incident beam comes in at the Bragg angle, and this produces strong diffraction out to the first ring that you see. The second ring corresponds to the 2nd order situation for above. The domains where the electron beam doesn't come in at the Bragg angle destructively diffract, so these don't blur the signal.
If you then think through all the possible ways you can orient the diffracting domains so that Bragg's law holds (you might need to draw this up), you get a ring.
micolich 1 month ago
@micolich For more info, try looking up the 'powder crystalline diffraction method', I think it was developed by Debye and ummm, Scherrer (or maybe its von Laue). You are right though, if you had a pure single crystal in there, you'd get an x-ray like diffraction pattern. Try looking at wikipedia's electron diffraction page for an image of this (youTube won't let me post the link).
micolich 1 month ago
@micolich Very nice question by the way!
micolich 1 month ago
Comment removed
freemanx2x 1 month ago
Thanks a lot for this great efforts.
lssam100 4 months ago
I have done this experiment in my Physics class a month ago and it is pretty cool but it also got me thinking and I know that I could be totally wrong but I have a few questions.
* Could the electron be radiating EM radiation that is causing the interference pattern?
* Has this experiment ever been done with neutrons?
* Does the 'matter wave' travel at the electron speed or the speed of light?
* Did the electron undergo quantum teleportation?
adam3141 9 months ago
@adam3141 Q1: No, because the light is emitted when the electron reaches the phosphor, so it does map where the electron hits the screen. Q2: Yes, it has, it has even been done recently with C60 (buckyballs). Q3: The speed of travel is a difficult one, I need many more characters to answer. Q4: No, the electron did not undergo quantum teleportation.
micolich 8 months ago
Excellent video! Thank you. You explained it perfectly.
moranginka 10 months ago
OMG which Idiot disliked this Video?? You just explained what my teacher failed to explain in a 2 hour lesson. Please Make More videos :)
Panzer0127 1 year ago
What about the observation problem? Can observation alter these results ? to show either way ? Sometimes it wants to be particle some times it behaves like a wave?
yourboycal 1 year ago
Excellent vid Adam. Cheers.
coburgmaths 2 years ago 2
Thanks. This is really usefull for my physics revision. :)
100greenbottles 2 years ago 2
Thanks for this video, it covered about 25% of my A-level syllabus in one go!
shadowplay1991 2 years ago 2
good job !!!
tmnagaraj 2 years ago 2
Great stuff!
tobywharne 2 years ago 5