Physics behind DVD's?

Question

I'm writing a (physics) paper on how dvd's and dvd players works in terms of an application of the wave nature of light. Does anyone know where I can find any information on these topics?

I checked Howstuffworks and wikipedia, but I didn't find anything particularity useful.

Answer 1

Does it have to be on DVD's? The principle that DVD players work on is not a very good example of the wave nature of light.

In a nutshell, a DVD player works by shooting a coherent beam of light (laser) at the surface of the disc. The surface of the disc is covered with ridges and pits. When the beam of light strikes a ridge, it is reflected back to a detector, and a digital "1" is recorded. When it strikes a pit, the light is not reflected, and a "0" is recorded.

Ignoring how impractical it would be, a beam of water could be used with a much larger, modified DVD, and the same results would be achieved.

To observe the wave nature of light, you would want to observe an instance of refraction, diffraction, interference, dispersion, or something of that sort.

There would be some refraction as the laser beam moves from the air into the plastic of the disc, and again as it came back out, but this has nothing to do with the principle a DVD works on. The pits and ridges on the disc generally do not cause any appreciable diffraction, ruling that out. Interference is not significant either, since the whole area is dark except for the light source. For the same reason (only one wavelength of light present), dispersion is unlikely.

So, I'm hard pressed to see how a DVD represents an application of "the wave nature of light". The only reason light is used is that it would be too difficult to fashion a needle (as in vinyl records) small enough to read the pits and ridges, and most other methods are impractical - except of course for magnetizing the disk surface, which is how computer hard drives work.

If I were you, I'd dissent a little and write about how a DVD player's read/write mechanism has very little to do with the wave nature of light, and much more to do with it's particle nature (such as requiring the light to travel in a perfectly straight line).