Question

A prism ABC, with base BC, is placed in four different orientations as shown. A narrow beam of white light is incident on the prism as shown. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?

A. (i)

B. (ii)

C. (iii)

D. (iv)

Answer 1

The third color from the top is blue. In the orientation (ii) the third color from the top is yellow as shown in the figure below.

Hence if the prism is inverted than the third color from the top is blue which is the color of the sky. Therefore, we get the orientation (i) as shown in the figure below