Young Double Slit Experiment Help

[Edgewood11]

I am trying to recreate the Young double slit experiment at my house with a laser. You could call it a homemade experiment I suppose. My question is if I use a laser pointer for my photon source what would I use as the photon detector. I want to have some sort of screen that can detect the photons as they hit the apparatus and then in return create a graph or data tale on my computer. Any ideas? I'm a junior in high school and extremely interested in the mysterious world of quantum physics.

 

[Simon Bridge]

You can use a normal screen for just looking at - get your experiment going with that before figuring out what sort of detector you want for your computer.

However, if you are serious, then you can get a digital oscilloscope for your computer which you can add electronic devices to to act as detectors.
For that matter - you can convert your sound-card mic input t act as a low V, audio frequency oscilloscope in software.

 

[Edgewood11]

Thanks! Any better ideas for my photon source? Id love to have a smaller stream of photons and it would amazing to be able to shoot individual photons

 

[Drakkith]

Maybe two polarizers set almost 90 degrees from one another? I think that might block almost all photons from getting through. Though with single photons you'd need a near perfectly light proof container along with something to detect the photons, such as a CCD or other digital imager.

 

[ZapperZ]

Thanks! Any better ideas for my photon source? Id love to have a smaller stream of photons and it would amazing to be able to shoot individual photons

It is one thing to show the 2-slit interference (easy). It is a different world when you want to do this one photon at a time. The latter is not trivial.

For example, this is a typical undergraduate experiment dealing with such a demonstration:

http://www.teachspin.com/instruments/two_slit/index.shtml

Not only do you need a single photon source, you also need single-photon detector! If you use light-sensitive plates, then you now have the added complexity of need to do this in a totally dark enclosure.

Zz.

 

[Claude Bile]

Welding goggles would be suitable as a high optical density filter as well.

On detection, a scattering screen and a CCD camera with a long exposure?

EDIT: Agree with ZapperZ; isolating the small signal from optical noise will be the biggest hurdle. Depending on photon flux, a CCD will probably need to be cooled. You can't beat a photomultiplier tube for sensitivity, but I'm guessing you don't have access to that.

Claude.

 

[Simon Bridge]

You can go a long way with backyard physics using surplus equipment, just google for Peter Terrin.

I think this is a case of: "how much money do you want to spend?"

 

[Edgewood11]

To be honest I'm only 17 and I have no formal education in physics. I'm simply amazed by the quantum world. Likewise, I barely comprehend many of the terms in the replies. I'm not familiar with an of the equipment you guys are talking about lol.

 

[Edgewood11]

Totally dark would be very challenging. The whole experiment may as well be performed within a dark box/container.

 

[Drakkith]

To be honest I'm only 17 and I have no formal education in physics. I'm simply amazed by the quantum world. Likewise, I barely comprehend many of the terms in the replies. I'm not familiar with an of the equipment you guys are talking about lol.

In that case I highly recommend just using a simple laser, double slit, and project it on the wall or simple screen.

Totally dark would be very challenging. The whole experiment may as well be performed within a dark box/container.

Yep. It would need to be in a container and you would need a digital camera or other device to detect the photons.

 

[Edgewood11]

Great video thanks but the only issue with that is i must find a dim light (easy) and dark box (easy) and a very sensitive light detector (hard and expensive).

 

[Drakkith]

Great video thanks but the only issue with that is i must find a dim light (easy) and dark box (easy) and a very sensitive light detector (hard and expensive).

I wonder if a cell phone camera could work? I barely use mine so I don't know if you can control things like shutter speed and exposure time and whatnot.

 

[Edgewood11]

A dark box and high exposure ccd sensor on a canon camera may be my best bet. As far as the single photon issue I think I have figured that out: use a very dim light source that only spits out a thousand photons a second. Sounds like a lot but light takes time to travel therefore it results in a single photon every .5 seconds.

 

[Edgewood11]

My dad has a very high tech camera that I could easily adjust the shutter speed. In fact, I've messed with the feature several times before.

 

[Drakkith]

I think you have your math a little wrong. 1 thousand photons per second would result in 1 photon every 0.001 seconds on average. Speed would not affect this.

 

[Edgewood11]

Yah I didn't even work it out I just guessed lol. The guy in the video gave the exact number but 1 photon every .001 seconds is actually not bad. It's closer to my 1 photon at a time goal. I can set the cameras shutter speed to capture a designated number of photons now that I know the frequency.

 

[Drakkith]

Have you considered a polarizer? Laser light should be all the same, so a single polarizer might be able to be rotated to block almost all of the light. Heck, a pair of polarizing sunglasses may work if the light is linearly polarized.

 

[Edgewood11]

What's the object of the polarizer? To make the stream of photons more concentrated? I just need help finding a dim light that would emit only 1000 photons a second

 

[Drakkith]

See here: http://en.wikipedia.org/wiki/Polarizer

Using a polarizer may block enough of the photons to reduce the rate to only a few photons per second. I don't know for sure if this would work in your setup, but I think it's worth a look.