# When the incidence angle is equal to the angle of refraction

In summary, at the interface of two different media, there is a certain angle of incidence where the incident ray passes straight through. This angle is equal to the critical angle of refraction, which can be found by using Snell's law. When the incidence angle is equal to the angle of refraction, the refractive indices of the two media are equal.

## Homework Statement

When the incidence angle is equal to the angle of refraction?

sina/sinb=n2/n1

## The Attempt at a Solution

I think as a=b => sina=sinb => n1=n2. We should have the same environment? But is that refraction?

At the interface of two different media, there is a certain angle of incidence where the incident ray just passes straight through. What is this angle?

blue_leaf77 said:
At the interface of two different media, there is a certain angle of incidence where the incident ray just passes straight through. What is this angle?
when b= pi/2 rad. It is the limit angle for a. sina=n2/n1

when b= pi/2 rad. It is the limit angle for a. sina=n2/n1
No, that corresponds to critical angle refraction. It very simple, you have Snell's law ##n_1 \sin a = n_2 \sin b##. Try to find a trivial angle ##a=b## which will make the left and right hand side of Snell's law equal irrespective of the refractive indices.

blue_leaf77 said:
No, that corresponds to critical angle refraction. It very simple, you have Snell's law ##n_1 \sin a = n_2 \sin b##. Try to find a trivial angle ##a=b## which will make the left and right hand side of Snell's law equal irrespective of the refractive indices.
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