NaBloPoMo Day #29 - Double Slit Experiment

by Nathan on Nov.29, 2009, under Brilliant Ideas

Image Credit: Patrick Edwin Moran - Wikimedia Commons

I’m sure you are familiar with Thomas Young’s Double Slit Experiment. I mean, who isn’t? In case you missed that day of modern physics in college, you can watch the video below to review.

Basically, if you shine light through one slit, the light acts like a particle, but if you shine light through two slits, it acts like a wave. What’s even stranger, is that if you shine one photon at a time towards two slits, it still acts like a wave. Even though it’s just one particle. But wait, there’s more! If you shine light at two slits, but you set up a detector to see which slit the light travels through, the light goes back to acting like a particle. It appears that light changes it’s behavior depending on how you observe it. Weird.

I want you to do a new experiment for me. Create two screens where when a photon hits the screen, a blip appears so that you know where the photon hit the screen. In one of these screens, cut out two slits. Then put the screen with the double slit in front of the other screen and shine a light, one photon at a time, towards the double slit. If the photon does not go through one of the slits, you will see a blip on the first screen. If it does go through one of the slits on the first screen, you will not see a blip on the first screen, but you will see a blip on the second screen. Repeat this experiment many times keeping track of the location of the blips on the second screen, then let me know what pattern appears. Will it be a wave interference pattern, or single particle created bands? My guess is an interference pattern. For bonus points, make the first double slit screen some type of powered detector that only detects photons when it’s on. Then turn it on and off to see if it changes the pattern on the second screen.

I know what you are thinking. Isn’t this like that experiment that has already been done where they put detectors in front of both slits of a double slit? NO!!!! The key to my experiment is that we detect whether or not a photon goes through a slit, but we have no information as to which slit it went through. If we knew which slit it went through, it would obviously act like a particle. Duh!

It is possible that this experiment, or an equivalent experiment, has already been performed. If so, please send me the results. If not, please perform the experiment and let me know what the pattern on the second screen is. The first person to provide me with results that are to my satisfaction wins a $10 gift card to either Runza or Sonny’s BBQ. Your choice.

3 Comments for this entry

Gregg
November 29th, 2009 at 6:44 pm
Well, I’m trying to set up this experiment in my secret sub-basement lab (closely modeled after Jimmy Neutron’s awesome lab). It would seem I am doing something wrong. Every time I fire the system up, it creates some kind of vortex. Now I can’t find my keys…or my cat. Maybe if I flip this switch in re
Obi
November 30th, 2009 at 11:10 pm
Ha ha ha! Good one, Greg!

Interesting thought there, Nathan. I, too, am now curious.

Oh, and by the way…you forgot “Day” in the title of yesterday’s post.
Nathan
November 30th, 2009 at 11:22 pm
Obi, thanks for pointing out the missing “Day”, I can’t believe I let that happen. I might have to yell at somebody in quality control.

Now that I think about it, I am pretty sure the experiment I described is the same as the standard double slit experiment, because if you shoot one photon at a time, you know whether or not it went through one of the slits by whether or not you see a blip on the screen. I am assuming that sometimes the photon doesn’t hit the screen in the standard double slit experiment. If not, that’s even more bizarre.

Now I want somebody to do a triple slit experiment where there is a detector in one slit. This way you know if the photon goes through that slit, or through one of the two other slits, or none of the slits. But, if it goes through one of the two non-detector slits, you don’t know which one it goes through. Will this produce a solid line and an interface pattern? Somebody try it and let me know. Thanks.