Question

Light enters from air into a slab having refractive index $1.50$. Speed of light in glass will be:

• A. $2\times {10}^{8}m/s$
• B. $3\times {10}^{8}m/s$
• C. $4.5\times {10}^{8}m/s$
• D. None

Answer 1

The correct option is A $2\times {10}^{8}m/s$

Refractive index of glass $=\frac{\text{Speed of light in air}}{\text{Speed of light in glass}}$
$1.50=\frac{3\times {10}^8}{\text{speed of light in glass}}$
Therefore, speed of light in glass $=\frac{3\times {10}^8}{1.50}m/s$.
$=2\times {10}^{8}m/s$