$\"\"$

The angle of incident beam is $\"\"$ .

The angle of refracted beam is $\"\"$ .

Snell $\"\"$ s law of refraction : $\"\"$ .

Since the the light wave passes through air, the refractive index is $\"\"$ .

Substitute $\"\"$ and $\"\"$ and $\"\"$ in the sell $\"\"$ s law.

$\"\"$

$\"\"$ .

The index of refraction of the material is $\"\"$ .

$\"\"$

The index of refraction of the material is $\"\"$ .