A thin prism `P_(1)` with angle `4^(@)` and made from a glass of refractive index 1.54 is comined 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. `5.33^(@)`
B. `4^(@)`
C. `3^(@)`
D. `2.6^(@)`

Answer

C

Explanation

Given `A=4^(@), mu=1.54, mu'=1.72, A'=?`
For no deviation, `(mu-1)A+(mu'-1)A=0`
`A'=-((mu-1)A)/((mu'-1))=((1.54-1)4^(@))/((1.72-1))=-3^(@)`
Nagative sign for connecting the two prisms in opposition.