Chapter 19, Problem 64A

To determine

The pattern of the spots that would be observed on the screen.

Explanation of Solution

Introduction:

Diffraction refers to a phenomenon where in light bends at the edge of an object due to which some of the light can be observed in the shadow region as well. When light passes through a diffraction grating, a pattern composed of light and dark bands can be observed on the screen.

The amount by which light diffracts depends on the wavelength of the light. As there is no diffraction at zero degrees, the yellow spot and blue spot would overlap and green spot would be visible.

Since the wavelength of blue light is shorter than that of the yellow light, the diffracted blue light spot would be observed closer to yellow spot i.e. at angle smaller than $+30°$ and $-30°$ .