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The angle of minimum deviation for a prism occurs when the angle of incidence and the angle of emergence are equal.
Let the angle of prism be A and the refractive index be n. Then, using the prism formula, we can write:
sin[(A+D)/2] / sin(A/2) = n
where D is the angle of deviation.
For the angle of minimum deviation, D is minimum, which means that sin(D/2) is minimum. This occurs when D is minimum, and for a prism of small angle, the minimum angle of deviation occurs when D = 0.
So, we have:
sin[(A+D)/2] / sin(A/2) = n sin(A/2) / sin(A/2) = n 1 = n
Thus, for a prism of refractive index 1.5, the angle of minimum deviation is equal to the angle of the prism. This means that A = sin-1(n) = sin-1(1.5) = 41.81 degrees.
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