Light

[Xain]

i plan on it lol

[Klaynos]

Have a look at the wikipedia link I put above...

 

The easiest form is shining a laser through 2 narrow slits.

[Kyrisch]

Since general use light sources (such as lightbulbs and flames and such) produce incoherent or not-all-in-phase light, and since only coherent light sources can completely destructively interfere (and produce said shadow) it will be difficult to make a flashlight "emit a shadow". Even with a laser, the wavelengths of visible light are so tiny that it is extremely difficult to make two light beams completely interfere using everyday stuff. The closest you can get is light and dark bands by shining a single coherent source through a number of slits spaced very close together.

[ydoaPs]

Since general use light sources (such as lightbulbs and flames and such) produce incoherent or not-all-in-phase light, and since only coherent light sources can completely destructively interfere (and produce said shadow) it will be difficult to make a flashlight "emit a shadow". Even with a laser, the wavelengths of visible light are so tiny that it is extremely difficult to make two light beams completely interfere using everyday stuff. The closest you can get is light and dark bands by shining a single coherent source through a number of slits spaced very close together.

 

Not to mention complete annihilation would be indistinguishable from emitting NOTHING AT ALL and thus would NOT be emitting a shadow.

[honestdude14]

..sounds alot like trying to create nothingness if you ask me.