Refraction of Light

Refraction of Light

The bedding of a light ray when it passes obliquely from one medium to another is called the refraction of light.

When a light ray passes through two different media, either of the media can be called a

• Denser medium: It is a type of medium in which the ray of light travels comparatively slower. Water is an optically denser medium in comparison with air.
• Rarer medium: Rarer medium is the medium in which the day of light travels faster. Air is an optically rarer medium in comparison with glass.

Laws of refraction of light

The laws of refraction of light are as follows:

• The incident ray, the normal ray, and the refracted ray lie on the same plane at the point of incidence.
• The ratio of the sine of the angle of incidence to the sine of the angle of refraction is always constant for a given pair of media.

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

This constant term ($\rm mu$) is called the refractive index. This law is also called as the Snell's law. The drawback of Snell's law is that when the ray passes through the normal, it doesn't bend and the angle of incidence becomes zero, i.e., $\rm i = 90^{o}$ and $\rm r = 0^{o}$.

At this condition, $\rm \frac{ \sin 90}{\sin 0} = \frac{1}{0} = \infty$

So, a revised formula for refraction is

$$\rm \begin{equation} \sin a \cdot n_{a} =  \sin b \cdot n_{b}  \end{equation}$$