View Full Version : Homemade Double Slit

2009-Apr-04, 11:04 PM
Or more appropriately titled, things I tried when bored:whistle:

Made from:

1 red laser pointing cat toy type thingy.
1 empty hard pack of cigs


Cut 3 sets double slits into one side of box, approx 1mm, 1.5mm and 2mm apart; towards the open end of the box.


Fire the cat laser toy through the sets of double slits and watch pattern on opposite inside of box from open end.


Definate Interference pattern showed with the 2mm double slit. Rather cool to be able to see this effect on ones own without investing a lot of money into it!

2009-Apr-05, 06:33 AM
It does not need to be laser. Any light source will do as long as you pass it through a single slit 1st (coherence (http://en.wikipedia.org/wiki/Coherence_length)is the key).

Try shining 2 lasers of identical make one through each (but not any other) of your 2/3 slits and see if they interfere (i.e. with each other).

2009-Apr-05, 08:56 AM
I did this once, with a laser pointer, and worked out the wavelength, roughly.

2009-Apr-05, 03:17 PM
I did this once, with a laser pointer, and worked out the wavelength, roughly.

The value can be quite accurate:

Thomas Young, an English Physicist in 1801, reported his experiment about the interference of light - when light was made to pass through a pin-hole and then through another two pin-holes side-by-side, a variation of intensity was observed on the screen.
Young's original experiments were performed with white light and he could deduce the values of wavelengths of extreme red and extreme violet lights from his observations, which were quite close to the accurate ones. (http://library.thinkquest.org/C006027/html-ver/op-inter.html)

2009-Apr-06, 02:31 PM
1 empty hard pack of cigs

tsk tsk.. thats not very healthy :lol:

maybe rename box from deck of cards :)

Would different wavelengths have the same effect (IR, UV, etc?) You can take a digital camera and see the IR coming from a TV remote. Would you see the same result if you replaced the laser pointer with the remote (taping down a button to cause the light to be on).