The Refractive Indices of Light and its relation with the Snell's Law

Light is both a particle and wave, it doesn't have mass but still interacts with other matter. These are few of the confused and oxymoronic statments you might be coming across in your Physics textbook.

The thing which makes everything visible is mostly invisible. (No, It's not crazy ... It's Physics😝)

Light is an entity , which is responsible for our existence, You literally won't be able to read this blog without this entity of physics. No wonder why physicist like Einstein and Newton spent majority of their life trying to study this incredible phenomena.

In this blog, we will try discussing about one of the properties of light out of the thousands discovered throught out human civilisation --- Light through different medium ...

Light travels in a straight line,

In the Rectilinear Propoagation of light, we learnt that light travels in a straight line (basically propogates rectilinearly) , hence we get sharp shadows of images, but this is true only when it travels in the same medium.

This is the typical image found in all Physics books under the Refraction of light chapter

Rarer to Denser -- Towards Normal

Denser to Rarer -- Away from the Normal

But have you wondered why it follows only this pattern?

One of the laws of refraction stated :-

* Sin of the angle of incidence by the sin of the angle of refraction is a constant for a given medium and colour of light, also know as Snell's Law. Also represented as:-

This constant is also known as the relative refrative index of medium 2 with respect to medium 1 of that set up.

(and to all who are wondering What is relative refractive index!?

It is the extent of change in direction travelled by light in the two mediums.)

So now,

hence we can say that , the product of sin of angle of incidence and absolute refractive index of medium 1 is always equal to sine of angle of refraction and absolute refractive index of medium 2.

We know that the absolute refractive indices of both the mediums are fixed and if we go with the example given above , Absolute refractive index of medium 2 > absolute refractive index of medium 1

hence the sin of both angles have to change accordingly to satisfy the above relations. (Kindly keep in mind that the sin Ө increases as Ө increases)

The more the refractive index, the lesser the angle has to be, to keep the equation true.

And the angle of incidence and refraction are calculated along the normal , If the medium has a greater refractive index than the first medium, the angle of refraction will be lesser than the angle of incidence, hence moves closer to the normal!

Similarly, if the absolute refractive index is lesser than the first medium, the angle of refraction is greater than the angle if incidence, hence moves away from the normal!!

Hence the light follows this specific pattern when moving from one medium to another.

Let's just hope this abstract entity doesn't decide to show another paradoxical version of itself to the scientists making them change this law again (after we finally understood it) 😜