A thin prism `P_(1)` with angle `4degree` and made from glass of refractive index 1.54 is combined with another thin prism `P_(2)` made from glass of refractive index 1.72 to produce dispersion without deviation. The angle of the prism `P_(2)` is

Options

A. `3^(@)`
B. `5.33^(@)`
C. `2.6^(@)`
D. `4^(@)`

Answer

A

Explanation

Angle of deviation `d=(n-1)A`
Dispersion produced by both the prism with be equal
`(n_(1)-1)A_(1)=(n_(2)-1)A_(2)`
`A_(2)=((n_(1)-1)A_(1))/((n_(2)-1))=((1.54-1)xx4)/((1.72-1))=3`
Hence, the angle of prism `P_(2)` is `3^(@)`