Question

Mark the correct statement/ statements:
a) Angle of incidence is equal to the angle of refraction.
b) Angle of refraction is smaller than the angle of incidence when light ray travels from the rarer medium to the denser medium.
c) Angle of refraction is greater than the angle of incidence when the light ray travels from denser medium to rarer medium.
A) a, b
B) b, c
C) a, c
D) All

Answer 1

We need to understand the angle relation between the incidence and refraction when the light rays move from one medium to another medium which has a different refractive index. This is achieved from Snell's law of refraction.

Complete step-by-step solution
We know that the refraction is the bending of the light rays due to the change in the densities of the media. The bending is dependent on the medium from which the light ray is coming and it is passing through. According to Snell's law, the ratio of the sines of the angle of incidence to the angle of refraction is equal to the ratio of refractive indices of the media. It is given as –
$\dfrac{\sin i}{\sin r}=\dfrac{{{\mu }_{2}}}{{{\mu }_{1}}}$
Where i is the angle of incidence,
r is the angle of refraction,
${{\mu }_{1}}$ is the refractive index of the first medium,
${{\mu }_{2}}$is the refractive index of the second medium.
We can see that the greater the ratio of the refractive indices the angle of incidence will be greater than the angle of refraction for angles lesser than ${{90}^{0}}$. i.e., when the light travels from a rarer medium to density the angle of incidence is greater than the angle of refraction. The light rays bend towards the normal.
When the light ray travels from a denser medium to a rare medium, the light ray bends away from normal making the angle of incidence lesser than the angle of refraction.
The colored medium denotes the denser medium in the below figure.

The correct answer is given by option B.

Note: The angle of refraction and the angle of incidence can be equal only if the light ray is passing through the normal or the refractive indices of the two media are the same. In all other cases, both of the angles will be different for the refraction of light.