Question

How does the angle of minimum deviation of a glass prism vary, if the incident violet light is replaced with red light?

• A. None of these
• B. Increases
• C. No change
• D. Decreases

Answer 1

Answer: (D)

Wavelength of red light is more than violet light.
Refractive index of a medium is different for light rays of different wave lengths. Larger the wavelengths, the lesser is refractive index.
Now angle of minimum deviation increases with increment in refractive index, $\delta =\left(\mu -1\right)\text{A}$
$\therefore$ Angle of minimum deviation for red light is less than the violet.