Find the dispersion produced by a thin prism of 18° having refractive index for red light = 1.56 and for violet light = 1.68.

4.16°    6.16° 2.16°    8.16°

2.16°

The dispersion produced by a thin prism is $\theta = (\mu_V - \mu_R)A = (1.68 - 1.56)18^o = 2.16^o$