Why is there a spectrum on the back of a CD or DVD?

[logearav]

Homework Statement

When i see the back of a CD or DVD, there is a spectrum, in which the various colours are overlapping with each other(continuous spectrum)

Homework Equations

What is the reason for this phenomenon, diffraction or dispersion?

The Attempt at a Solution

Diffraction means bending of light around the edges of obstacles and Dispersion is splitting of white light into its constituent colours or wavelength.
I presume the tracks and sectors present in CD or DVD acts as slits and rulings akin to grating element. Am i correct? Pls help revered members.

 

[ehild]

It is diffraction, there are rulings on the CD, so it acts as a diffraction grating. See: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/grating.html#c2

ehild

 

[logearav]

Thanks a lot ehild