Deviation in Reflection, Refraction and Prism

Shikhar was playing with a torch by projecting its light on different surfaces.

He noticed that some surfaces had diverted the path of light.

And some surfaces are reflecting the light in the same media. Such as a mirror.

And some deviated the path of light and passes through the medium. such as water and glass slab.

He was surprised about the behavior of light that how the same light posses different behavior with different surfaces.

He was curious to know the reason behind that.

Let's try to help him out to find the behavior of light on different surfaces.

When light falls on the opaque object, it reflected in the same media by following the laws of reflection.

The first law of reflection states that the angle of reflection equals the angle of incidence.

And the second law of reflection states that the incident ray, the reflected ray, and the normal to the reflecting surface at the point of incidence lie in the same plane.

And when the light falls on the transparent medium it deviated from its path and passes through the other medium.

While passing through the medium it deviated from its path. This phenomenon is called the refraction of light.

The refraction of light also follows two laws.

According to the first law of refraction, the incident ray, the refracted ray and the normal to the interface at the point of incidence, all lie in the same plane.

And the second law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

Further, we will analyze the deviation of light through reflection, refraction, and prism.

Let's find the deviation of light through reflection, refraction, and prism.

Let's consider the deviation by the reflection of the light through the plane mirror.

Let, light incident at $\angle i$ and reflected by making an $\angle r$ with normal.

The angle of deviation is the deviation in the light rays from its path and is given by $\delta$.

We can easily plot the graph between angle of incidence and the deviation of light in reflection.

Now, let's analyze the deviation of light in refraction.

Let, a light from medium $1$ goes to the medium $2$.

The refractive index of medium $2$ is greater than the refractive index of medium $1$.

The angle of incidence is $\angle i$ and the angle of refraction is $\angle r$.

And $\delta$ is the deviation in the path of light.

In refraction, we cannot be able to plot a graph between angle of incidence and deviation.

Because the relation between incidence angle and deviation cannot be calculated.

Further, we'll find a deviation plot in the prism.

Let, the minimum deviation of the prism is ${\delta }_m$.

The refractive index of the prism is given by $n_{21}$ as $A$ and ${\delta }_m$ can be measured experimentally.

For a small angle prism. i.e., a thin prism ${\delta }_m$ is also very small, and we get.

The variation in deviation of light with respect to incident light is given by the plot above.

This is all about the deviation in reflection, refraction, and prism.

Revision

The plot of the graph between the angle of incidence and the deviation of light in reflection.

The graph plot between incident angle and deviation angle of light in the prism.

The end