A material is embedded between two glass plates. Refractive index n of the material varies with thickness as shown below. The maximum incident angle (in degrees) on the material for which beam will pass through the material is-

Options

A. 60
B. 53.1
C. 43.5
D. 32.3

Answer

B

Explanation

`1.5 xx sin i= 1.2 " sin r " rArr "sin r " = (1.5)/(1.2) `sin i
TIR should not take place `therefore sin r lt 1 `
`(1.5)/(1.2) lt sin i lt 1 `
`sini lt (12)/(15) rArr sin i lt 0.8 rArr sin 45^(@) = (1)/(sqrt(2)) = 0.707`
`" " rArr i_(max) gt 45`.