Help with double-slit experiment

This isn't really homework so please let me know if I've posted this in the wrong place. We've been given the task of carrying out an experiment on pretty much any topic. I've chosen young's double slit experiment to show that light has wave-like properties, and i'm also going to use the equation to calculate the unknown wavelengths of some light sources.

I have everything I need except the double slit. So my question is, is there anywhere to buy a premade double slit? This is the best I can find, except with postage it comes to £30... which is way too much I think. http://www.3bscientific.co.uk/diaphragm-with-4-double-slits-of-different-spacings-u14101,p_83_113_872_1049.html?initOptionReferer=1

Does anyone know of any other website or way of doing it? Thanks for any help.

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First of all, please let me know if any of this is wrong as I'm still quite new to it. I was able to set something up to produce this at home:

I want to calculate the wavelength of different light sources using the equation λ = y • d / (m • L), where

d = Distance between slits
L = Distance from slits to screen
y = Distance from central fringe
m = Fringe order value

d and L are easy enough. But for m, can I choose the 3rd, 4th or any fringe I want and use that in the calculation, basing y on the fringe I select? Also for y, i'm a bit confused in how to measure the distance between it and the central fringe. From which points do I measure exactly?

hello,

you have done very well with your experimental set-up; it looks beautiful.

i was going to tell you that a piece of paper and a razor blade will do the trick, but you have done very well with what ever you have used. (what are you using by the way?)

for the calculation, feel free to choose any m you want, but i would keep it small so you don't measure the 11th spot and use m=12 in your calculations!

to measure y, measure from the center of the central spot to the center of the bright spot you have chosen.

good luck.

hello,

you have done very well with your experimental set-up; it looks beautiful.

i was going to tell you that a piece of paper and a razor blade will do the trick, but you have done very well with what ever you have used. (what are you using by the way?)

for the calculation, feel free to choose any m you want, but i would keep it small so you don't measure the 11th spot and use m=12 in your calculations!

to measure y, measure from the center of the central spot to the center of the bright spot you have chosen.

good luck.
Thanks for clearing it up! All I used was a piece of metal with a slit in it (used for light experiments in class). I put a sewing needle inbetween to divide it into 2 slits then aimed a laser pointer at it. It's this:

brilliant! well done.