Question

A ray of light in air strikes a block of quartz at an angle of incidence of 30 degrees. The angle of refraction is 20 degrees. What is the refractive index of quartz?

Answer 1

Given:

Angle of incidence = 30 degrees

Angle of refraction = 20 degrees

To Find: Refractive index of quartz

Calculation:

• Refractive index (n) of any medium is defined as ratio of speed of light in vacuum (c) to the speed of light in medium (v).
• Refractive index is also given as sine value of angle of incidence divided by sine value of angle of refraction.
• Refractive index, $n=\frac{sin i}{sin r}$
• $n=\frac{sin 30}{sin 20} =\frac{0.5}{0.34} =1.47$
• Angle of refraction is less than angle of incidence which means, the light ray is travelling from rarer medium to denser medium.

Answer:

Value of refractive index is 1.47.