The figures represent three cases of a ray passing through a prism of angle $A$. The case corresponding to minimum deviation is

$A$ certain prism is found to produce a minimum deviation of $38^{\circ}$. It produces a deviation of $44^{\circ}$ when the angle of incidence is either $42^{\circ}$ or $62^{\circ}$. What is the angle of incidence when it is undergoing minimum deviation (in $^{\circ}$)?

An equilateral prism $P$ produces a minimum deviation for a given light ray. Additional prisms $Q$ and $R$ of the same shape and material are placed as shown in the figure. The ray will experience:

For a small angled prism with prism angle $A$,the angle of minimum deviation $(\delta_m)$ varies with the refractive index $(\mu)$ of the prism as shown in the graph.

If the angle of minimum deviation of a prism is $30^o$,the angle of incidence is $60^o$,and the prism angle is $30^o$,then the refractive index of the prism is:

On an equilateral prism,it is observed that a ray strikes grazingly at one face and if the refractive index of the prism is $2$,then the angle of deviation is $........^o$.