Question

A ray of light incident at an angle `theta` on a refracting face of a prism emerges from the other face normally. If the angle of the prism is `5^@` and the prism is made of a material of refractive index `1.5`, the angle of incidence is.
A. `7.5^@`
B. `5^@`
C. `15^@`
D. `2.5^@`

Answer 1

Correct Answer - A
Here, `A = 5^@, mu = 1.5, i_1 = ?`
As the ray emerges from the other face of prism normally,
`i_2 = 0^@ :. r_2 = 0^@`, Fig.
As `r_1 + r_2 = A`
`r_1 = A - r_2 = 5 - 0 = 5^@`
From `mu = (sin i_1)/(sin r_1), sin i_1 = mu sin r_1 = 1.5 xx sin 5^@`
=`1.5 xx 0.087 = 0.1305`
`i_1 = sin^-1 (0.1305) = 7.5^@`.
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