What is responsible for streaks of coloured light from a compact disc ?

Explanation

The streaks of coloured light reflected from a compact disc (CD) resemble the colours that appear when white light passes through a prism. However, a CD does not separate colours on account of refraction. Instead, the light waves undergo interference here.
The digital information (alternating pits and smooth reflecting surfaces on the CD) forms closely spaced rows. These rows of data do not reflect nearly as much light as the thin portions of the disc that separate tham. So light reflected from tham undergoes constructive interference in certain directions and destructive interference in certain other directions. The constructive interference would depend upon wavelength of light, orientation of CD and direction of incoming light. Thus when white light is reflected from the CD, each wavelength of light would be seen at a particular angle w.r.t. teh surface of CD. That is how we observe streaks of coloured light from the CD.