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Physics - Optics

You will get some questions about reflection, refraction, mirrors, and lenses. All of these stuffs put together means optics. 

Optics involved light and we have already discussed light. We said earlier that light travels at a speed of three times ten to the eight meters per second. This is only true for light traveling in a vacuum. 

When light travels through an actual medium like air, water, or etcetera, it travels slower. Every medium has something called a refractive index, which tells how much slower light travels when it is in that medium than it does when it is in a vacuum. 

Rule number 44: 
Index of refraction, a medium’s refractive index equals the speed of light in a vacuum divided by the speed of light in the medium or n=c/v. When a ray of light is passing through one medium and is reflected from another, the angle at which it hits the new medium is equal to the angle at which it bounces off. In other words, the angle of incidence is equal to the angle of reflection. 

Sometimes a ray of light may hit a medium and not be reflected. This light will go right through the medium. However, once it hits the medium, it bends. This bending is called refraction. 

There is a rule that we can use to figure out the angle of refraction. The rule is called Snell’s Law. 

Rule number 45: 
Snell’s Law, n1sinθ1 = n2sinθ2 where n equals the index of refraction for the medium.