Question

A thin prism of angle 6° and refractive index for yellow light (nY)1.5 is combined with another prism of angle 5° and nY = 1.55. The combination produces no dispersion. The net average deviation (δ) produced by the combination is (1/x)°. The value of x is __________.

Fig. Prism

Answer 1

The correct answer is 4
$δ_{net} = δ_1+δ_2$
$= |(µ_1-1)A_1-(µ_2-1)A_2|$
$= |3°-2.75°|$
$δ_{net} = \frac{1°}{4}$
⇒ x = 4