Question

Two beams of red and violet colors are made to pass separately through a prism (angle of the prism is ${{60}^{0}}$). In the position of minimum deviation, the angle of refraction will be
A. 30º for both the colors
B. greater for the violet color
C. greater for the red color
D. equal but not 30º for both the colors

Answer 1

Hint:Red color or any other color, is determined by a unique wavelength. We know that white light consists of seven colors and when it is passed through the prism it gets split into seven colors. Also, the prism is a device for splitting the white light. Also, in case of angle of minimum deviation both the angle of the incident and exiting rays form equal angles with the prism faces.

Complete step by step answer:
The angle of the prism is the apex angle of the prism and it is here ${{60}^{0}}$. When the angle of deviation is equal to the minimum then, the angle of incidence at which the light enters the prism and the angle at which the light exits both are equal.
Thus, ${{r}_{1}}={{r}_{2}}=\dfrac{A}{2}=\dfrac{60}{2}={{30}^{0}}$
Thus, the angle for both the colors comes out to be \[{{30}^{0}}\].

Hence, the correct option is A.

Note:The condition of minimum deviation occurs when the path of the light inside the prism is parallel to the base of the prism and If the incident light beam is rotated in either direction, the deviation of the light will be higher from its incident path. Unless we are given anything, we assume that the medium surrounding the prism is vacuum. Also, Angle of refraction is independent of the color.