The young's double slut experiment is pretty awesome i guess.. i never had thought that light + light could ever equal dark.. so I wanna try and do the double slit experiment myself. For the slits and the curtain.. i'm thinking of using Aluminum foil into which i can cut fine slits with a razor blade. I have around 6-7 meters [lengthwise] free space available. Which makes my D = 7.00 m. If i keep the slits like.. 3 mm across [i doubt if i can get it even that fine].. I get the fringe width as [itex]2333.33\lambda[/itex]. So, what wavelength of light should I use? Also, how can i get such a light source? The problem is that the wavelength i'm getting so that i can see the fringes clearly is to the order of tens of micrometer.. what i need is something in the order of hundreds of nanometer [i guess].. so.. basically.. i'm missing out on a [or two] factor of ten. any suggestions?