Question

The speed of light in air and glass is $3\times {10}^8$ m/s, and $2\times {10}^8$ m/s respectively. A beam of light falls on a glass at an angle of ${30}^o$ with surface. The angle of refraction in glass is

• A. ${25}^o{16}^{\prime }$
• B. ${35}^o{16}^{\prime }$
• C. ${15}^o{26}^{\prime }$
• D. ${30}^o{16}^{\prime }$

Answer 1

The correct option is A ${25}^o{16}^{\prime }$

Refractive index $=\frac{Speedlightinvaccum}{Speedoflightinglass}{\eta }_{glass}=\frac{3\times {10}^8}{2\times {10}^8}=\frac{3}{2}=1.5$

According to snails law

$1\left(\sin 30°\right)=1.5\left(\sin \theta \right)\sin \theta =\frac{1}{3}=0.33$

As $0.33<0.5\theta <30°$

Approximate value $\theta =25°{.16}^{\prime }$