Angle of minimum deviation equals prism angle minus half angle of minimum deviation. This specific angle ensures minimum deviation in prism experiments.
The angle of minimum deviation for a light ray passing through a prism occurs when the ray is incident on the first surface of the prism at an angle that is equal to the angle of refraction at the second surface.
This condition can be found graphically by plotting the angle of incidence versus the angle of deviation for a range of prism angles.
As the prism angle increases, the angle of incidence at which minimum deviation occurs also increases.
The angle of minimum deviation itself decreases as the prism angle increases.
The condition of minimum deviation can be expressed mathematically as follows:
δD = 2A - 2α
where:
δD is the angle of minimum deviation
A is the prism angle
α is the angle of incidence
This equation can be rearranged to solve for α:
α = A - δD/2
This equation shows that the angle of incidence at which minimum deviation occurs is equal to the prism angle minus half the angle of minimum deviation.