Question

(a) How does the deviation produced by a prism depend on
(i) the refraction index of its material, and
(ii) the wavelength of incident light

(b) How does the angle of minimum deviation produced by a prism change with increase in (i) the wavelength of incident light and (ii) the refracting angle of the prism?

Answer 1

(a)

(i) The prism with a higher refractive index produces a greater deviation than a prism with a lower refractive index for a given angle of incidence.

(ii) The refractive index of a given transparent medium is different for the light of different colours. It decreases with the increase in the wavelength of light. Thus the refractive index of the material of a prism for visible light is maximum for the violet colour and minimum for the red colour. Hence, a given prism deviates the violet the most and the red light least.

(b) (i) As we increase the wavelength of incident light, the angle of deviation decreases.

(ii) The angle of deviation increases with the increase in the refracting angle of the prism