Question

What is the condition for dispersion without deviation?

(a) δ-δ’=0

(b) δ+δ’=0

(c) δ × δ^‘=0

(d) \(\frac {\delta}{\delta^{‘}}\)=0

This question was posed to me during an interview for a job.

The query is from Ray Optics topic in division Ray Optics and Optical Instruments of Physics – Class 12

Answer 1

Correct answer is (b) δ+δ’=0

The explanation is: Consider combining two prisms of refracting angles A and A’, and dispersive powers ω and ω’ respectively in such a way that their refracting angles are reversed concerning each other. For no deviation, the condition is:

δ+δ’=0

So, (μ-1)A+(μ’-1)A’=0  or  A’=-\(\frac {(\mu -1)A}{(\mu^{‘}-1)}\)