Chapter 24, Problem 23Q

To determine

To explain: The phenomenon behind the reflected light to be full spectrum when a compact disk is held at an angle in white light. Also, the pattern observed when monochromatic light was used.

Explanation of Solution

Introduction:

A large number of parallel slits which are equally spaced can be defined as diffraction grating. Diffraction grating is of two types: transmission and reflection grating.

If a CD is observed closely, it can be seen that there are various spiral patterns including the alternating raised as well as flat areas on it. The top surface is referred as pits while the spaces between the pits are called as lands. The pits and lands can be considered as slits in the diffraction grating. So, when the CD is held at an angle in white light, then the pits and lands will diffract the light and hence produces the diffraction pattern. In case of monochromatic light, a single wavelength of interference pattern is formed.

Hence, if the monochromatic light was used, diffraction grating is seen.