There's one angle of incidence β onto a prism for which the light inside an isosceles prism travels parallel to the base and emerges at angle β.
Find an expression for β in terms of the prism's apex angle α and index of refraction n.
The Attempt at a Solution
to Use refraction law: n1sin(betta1)=n2sin(betta2). Then express betta2 through alpha. But i am not getting the right answer