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Refraction of Light

You must have heard of reflection of light. It's when a ray of light bounces back from a surface. 

When a light ray hits a mirror, it bounces back with the same angle as the angle with which it hit the mirror. The angle of incidence is always equal to the angle of reflection


But what if instead of a mirror, there is a transparent surface?
In such cases, the light ray goes through the surface, and undergoes refraction. 


What is refraction?
Refraction is the bending of light when it goes from one medium to another. This happens because the speed of light changes across two different media.

When a ray of light is perpendicular to the normal, it travels to the other medium without bending. The ray of light only bends when it goes obliquely from one medium to another.

This bending of light depends on the medium through which light is travelling.


Optical Density

• Rarer medium:  The medium through which the speed of light is more is an optically rarer medium.

• Denser medium: The medium through which the speed of light is less is an optically denser medium.

Note: optical density does not depend on the actual density of the material.


When a ray of light goes from a rarer medium to a denser medium, it's speed decreases and it bends towards the normal. So the angle of refraction is lesser.

Similarly, when the ray of light goes from a denser medium to a rarer medium, it's speed increases and it bends away from the normal. This means that the angle of refraction will be more.


I had mentioned earlier that refraction of light occurs because of the change in the speed of light as it travels from one medium to another. Even though the ray of light doesn't bend when it's perpendicular to the normal, the speed of light still changes.

But why does the change in the speed of light make the ray of light bend? What does this have to do with the optical density?

In order to understand this, let's replace the ray of light with a car and the two media with roads, one road which is smooth(optically rarer medium), and one road which is rough and rocky(optically denser medium). When the car travels from the smooth road to the rocky road, the speed of the car will decrease.

Now imagine the car going from the smooth road onto the rocky road obliquely. One corner of the car will hit the rocky road before the other, which means that a portion of the car will actually be travelling faster than the other, which has reached the rocky road.

Because of this increase in speed, this portion of the car will cover larger distance and the portion of the car which is on the rocky road will cover a shorter distance in the same time, and this makes the path of the car bend.

This should give you a better idea on why refraction of light happens.


Thank you for reading.

- Arya Bharaty


Comments

  1. AnonymousNovember 5, 2022 at 11:05 AM

    I read this when time didn't exist, but when I'm typing time is existing in relation to me the time exists. But without me, time cannot exist.

    ReplyDelete

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