Refraction Of Light - Practice Questions & MCQ

Refraction

Deviation or bending of light rays from their original path while passing from one medium to another is called refraction. It is due to change in the speed of light as light passes from one medium to another medium. If the light is incident normally then it goes to the second medium without bending, but still, it is called refraction. When a light ray passes from one medium to another such that
it undergoes a change in velocity, refraction takes place. Hence, the wavelength of light changes, but frequency remains the same.

Types of medium: 

1.  Rarer medium: Medium in which the speed of light is more is called optically Rarer medium. 
2.  Denser medium: Medium in which light travels more slowly is called optically denser medium.

Refractive index: Refractive index of a medium is defined as the factor by which speed of light reduces as compared to the speed of light in vacuum.

                                 $\mu=\frac{c}{v}=\frac{\text { speed of light in vacuum }}{\text { speed of light in medium }}$

 When light moves from denser to a rarer medium, it bends away from the normal.

 When light moves from rarer to denser medium, it bends towards the normal.

Laws of refraction: 

1. The incident ray, the normal to any refracting surface at the point of incidence, and the refracted ray all lie in the same plane called the plane of incidence or plane of refraction.
2. The ratio of sine of angle of incidence to the angle of refraction is always constant. 

                           $\frac{\sin i}{\sin r}=$ constant

Also, $\frac{\sin i}{\sin r}=\frac{\mu_2}{\mu_1}=\frac{v_1}{v_2}=\frac{\lambda_1}{\lambda_2}$
For applying in problems remember

$$
\begin{aligned}
& \mu_1 \sin i=\mu_2 \sin r \\
& \frac{\sin (i)}{\sin (r)}=\mu_{21} \quad=\text { refractive index of the second medium with respect to the first medium. }
\end{aligned}
$$

Deviation due to refraction:
Deviation $(\delta)$ of ray incident at $\angle i$ and refracted at $\angle r$ is given by :

$$
\delta=|i-r|
$$