How does the angle of deviation formed by a prism change with the increase in the angle of incidence ?
Draw a graph showing the variation in the angle of deviation with the angle of incidence at a prism surface.

Explanation

The angle of deivation (`delta `) produced by a prism first decreases with the increase in angle of incidence (i) and reaches to a minimum value at a eartain angle of incidence. With further increase in angle of incidence, angle of deviation also increases. The figure alongside shows the variation of angle of deviation with angle of incidence.