This 'ible will show two simple methods to make a double-slit, that is small enough to create an interference pattern.

Interference is an effect waves show, when they interact with each other. If two (or more) waves have the same wavelength and a fixed phase relationship they are called "coherent". And if such coherent waves hit the same spot, they can support each other, annihilate each other (yes, you did read right: light + light = more light or no light) or something in between depending on their phase difference. The special thing about laser light is its huge coherence length meaning the light emitted by a laser is practically always coherent. A double-slit (or better a lattice) splits up the laser beam into two (or many) "beams". Beyond the double-slit or lattice each new "beam" spreads in every direction interfering with the other one(s). This creates a characteristical pattern of maxima and minima: the interference pattern. For further information have a look at the wikipedia articles about the double-slit experiment and interference.

Disclaimer: This instructable presupposes responsible handling of laser sources. DO NOT DIRECTLY LOOK INTO ANY LASER BEAM. Always handle laser beams with caution. I'm not responsible for any injuries (e.g. damaged or blinded eyes) due to wrong handling of your laser source.

Step 1: Double-slit Out of Paper: Materials

We'll start with a fast, but pretty low quality double-slit out of paper.

What you need is:
  • a small sheet of paper
  • sharp scissors
  • a black marker
<p>Does it work with a laser pointer?</p>
I really made it for my project and got A+ in my result
Hi. I just performed the double slit experiment and this is what I saw. Am I doing anything wrong?
Because you are watching them<br><br>Reply if u didn't understand the joke
<p>Yes , you did the slits to big , its suppose to be a this line from the laser. </p>
<p>Hey there,</p><p>I am creating a spectroscopy laboratory for students as part of my thesis paper and i want to do this double slit experiment. Now my results are not very clear (the lines are not very defined). Can anyone give me any tipps on how i can get better results? :D Thanks a lot !!!</p>
<p>I did the foil version, worked right off the bat. I managed to put 6 meters between the foil and the wall so I got nice separation.</p>
<p>Made a simpler version, but still worked. Using the aluminum foil was a great idea, thank you!</p>
thanks.Your site is very excelent ,&amp; usuful. be success
Back in the 1960's we used stacked razor blades to cut or scratch paralel slits in graphite on microscope slides to measure the wavelength of light. Two blades, two slits- three blades, three slits ect.
This is pretty cool. I made my own slits not too long ago using a very similar method. Getting the slits to be parallel and very close together was a little tricky. I eventually tried using mechanical pencil graphite as a spacer. I made the slits by cutting up against the graphite and it worked pretty well. For my next experiment I am going to use commercially available slits that are scratched into glass slides. They're cheap and well calibrated.

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