Polaroid Ka Gyan...

 Hello Readers,

Have you ever heard of Polaroid glasses being used in goggles? Do you know, how these glasses protect our eyes? Let us discuss.

The light produced by all the natural sources of light such as sun, stars, etc. is unpolarized (A light is said to be unpolarized if the oscillation of electric field vectors is not confined to a single plane).

So, what happens when the unpolarized light passes through a polaroid?

1. The unpolarized light becomes plane polarized (A light is said to be plane-polarized if the oscillations of electric field vectors are confined to a single plane).

2. The intensity of plane-polarized light becomes half of its initial intensity.

Please refer to the diagram shown below:

We can easily notice that the oscillations of the electric field vector parallel to the pass axis are crossing the Polaroid whereas all other oscillations are getting absorbed by the Polaroid.

Now let us understand how it helps in designing goggles.

How do we see an object?

For us to see an object, we must receive the light reflected from the surface of the object. Is this sufficient for us to see that object? No, there are other factors too.

If the intensity of light that enters our eyes is more, due to the glare, we will not be able to see the object clearly. Think of glare from a shiny object, isn’t the visibility less?

How do Polaroid glasses help us?

Polaroid glasses reduce the intensity of the light entering our eyes. This in turn helps us to see the objects clearly.

Additional Information about Polaroids:

In the above discussion, we saw how Polaroids can reduce the intensity of unpolarized light to help us see. Now let us see the effect of Polaroids on plane-polarized light. The explanation for this was given by Malus, through his famous law called Malus’s Law.

According to this law, if a plane-polarized light of intensity is passed through a Polaroid, then the intensity I at the output of the polaroid is given by.

Here,  is the angle between the pass axis of the Polaroid and the plane of polarization of the incident light. Please refer to the diagram shown below:



Interesting Fact:

A company called Polaroid designed the original polarizing filter. The same company developed the first sunglasses with polarizing filters and the first instant film cameras.