Question

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

• A. 60.0
• B. 53.1
• C. 43.5
• D. 32.3

Answer 1

Answer: (B)

Light beam passes through material, if no total internal reflection occurs at surface of material
$So, \sin\, i \le\frac{n_{2}}{n_{1}}$
$\Rightarrow \sin i \le\frac{1.2}{1.5}$
$\Rightarrow \sin\, i \le0.8$
or $\sin{\left(i_{\text{maximum}}\right)}=0.8$
$\Rightarrow i_{\text{maximum}}=sin^{-1}\left(0.8\right)$
$\Rightarrow i_{\text{max}}=53.1^{\circ}$