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

For dispersion without deviation
`delta_(1)=delta_(2)`
`A_(1)(mu_(1)-1)=A_(2)(mu_(2)-1)`
`10(1.42-1)=A_(2)(1.7-1)`
`A_(2)=6^(@)`