Can the angle of refraction be equal to the angle of incidence?

[bobaustin]

Snell's law says
n1sin(theta1) = n2sin(theta2)

The angle of refraction theta2 can be greater or less than the angle of incidence theta1. That's fairly obvious.

My question is if theta2 = theta1 then we don't have an interface (because n1 = n2) so the light is still in the same medium, and there is nothing to talk about?

Is there a case where there is an interface and theta2 = theta1 ?

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I think I found the answer: Pyrex rod in Wesson oil!

 

[Doc Al]

You can always pretend that there's an interface, with each side having the same n. Snell's law then tells you that θ₁ = θ₂, which makes sense since it just means that the light continues straight through as if there was no interface (which there isn't, of course).

 

[ideasrule]

You can always pretend that there's an interface, with each side having the same n. Snell's law then tells you that θ₁ = θ₂, which makes sense since it just means that the light continues straight through as if there was no interface (which there isn't, of course).

How about the case that the OP pointed out: two transparent substances with the same index of refraction?

Of course, angle of incidence is also equal to the angle of refraction with the former is 90 degrees.