# Refraction of light through a prism

Discussion in 'Physics' started by logearav, Oct 9, 2011.

1. ### logearav Thread Starter Member

Aug 19, 2011
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Revered members,
Please see my attachment which deals with refraction of light through a prism. PQ is incident ray, QR is refracted ray and RS is emergent ray. i1,i2 are angles of incidence. i1 is angle of incidence, but how i2 qualifies to angle of incidence. Similarly how r2 is angle of refraction? Please help members

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2. ### steveb Senior Member

Jul 3, 2008
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469
I agree with your point. You would expect i2 to the the refracted angle and r2 to be the incident angle. But, don't worry about this because these are simply labels and one is free to label angles with any variable name.

There is one sense in which you can say that the emergent ray is an incident ray. That it, light rays have the property that they can be reversed in time. So you could solve the problem as if the ray went in on the right side and came out on the left side. But, then you would expect r1 to be the incident angle and i1 to be the refracted angle.

Aug 19, 2011
248
0