Problems on Total Internal Reflection in Prism

The optical fibre work on the principle of total internal reflection

We all access the internet on our laptop or PC.

The laptops are connected with the help of optical fibers which is provided by the internet service provider.

We use optical fiber in communication because there are large bandwidth and minimum loss in power transmission.

The optical fibre work on the principle of total internal reflection.

Next, we will discuss in detail about total internal reflection.

Let's discuss total internal reflection in detail

Total internal reflection is the complete reflection of a ray of light within a medium.

Such as when the light goes from water or glass to the air then it returns back to water or glass.

For example, the incident light goes from denser to rarer and refracted ray deviated away from normal.

And again when we increase the angle of the incident, then the angle of refraction of becomes

In this case, the angle of incidence is equal to the critical angle and it makes grazing emergence.

And if the angle of incidence is greater than the critical angle then incident light totally reflects in a denser medium that is called total internal reflection.

Next, we will solve the problem based on total internal reflection in the prism.

Let's solve a numerical problem based on total internal reflection in the prism.

Let's take a right-angled triangular prism whose refractive index is .

In 2-D, the prism looks like as,

A Light is incident from the air at an angle on the side PQ and goes to a denser medium prism.

It does not deviate inside the prism and goes to side PR.

Here, light undergoes total internal reflection in the prism at face PR,

And has a minimum value of 45°.

Then, we need to find the angle of the prism.

Now, we apply snell's law, when has a minimum value of and the refractive index of a prism is .

Here, we get the value of

now, we have to find the angle of prism θ.

To fulfil the condition of total internal reflection,

The critical angle must be greater or equal to and the angle of prism .

Revision

Total internal reflection is the complete reflection of a ray of light within a medium.

The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle.

Here incident ray goes from air of refractive index n1 to water of refractive index n2.

The formula of Snell's law.

The End