A thin prism having refracting angle `10^(@)` is made of glass of refracting index `1.42`. This prism is combined with another thin prism of glass of refractive index `1.7`. This combination produces dispersion without deviation. The refracting angle of second prism should be `:`

Options

A. `6^(@)`
B. `8^(@)`
C. `10^(@)`
D. `4^(@)`

Answer

A

Explanation

The condition for dispersion without deviation is given as `(mu-1)A=(mu.-1)A.`
Given `mu=1.42,A=10^(@),mu.=1.7,A.= ?`
`:.(1.42-1)xx10=(1.7-1)A.implies(0.42)xx10=0.7xxA."or", A.=(0.42xx10)/(0.7)=6^(@)`