**i. **Variation of angle of incidence i with angle of deviation δ is as shown in figure.

**ii.** It shows that, with increasing values of i, the angle of deviation δ decreases initially to a certain minimum (δ_{m}) value and then increases.

**iii. **The curve shown in the figure is not a symmetric parabola, but the slope in the part towards right is less.

**iv.** Except at δ = δ_{m} there are two values of i for any given δ. From principle of reversibility of light, we can conclude that if one of these values is i, the other must be e and vice versa.

Thus at δ = δ_{m}, we have i = e.