$A$ glass prism $A$ deviates the red and blue rays through $10^{\circ}$ and $12^{\circ}$ respectively. $A$ second prism $B$ deviates them through $8^{\circ}$ and $10^{\circ}$ respectively. The ratio of their dispersive powers is ($A$ to $B$):

The refractive index of the material of a prism is $\sqrt{2}$ and the angle of the prism is $30^{\circ}$. One of the two refracting surfaces of the prism is made a mirror inwards,by silver coating. $A$ beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface) if its angle of incidence on the prism is (in $^{\circ}$)

Angle of minimum deviation for a prism of refractive index $1.5$ is equal to the angle of prism. The angle of prism is $......^{\circ}$ $\left(\cos 41^{\circ}=0.75\right)$

$A$ ray falls on a prism $ABC$ $(AB = BC)$ and travels as shown in the figure. The minimum refractive index of the prism material should be

In the diagram,the ray passing through the prism is parallel to the base. The refractive index of the material of the prism is:

The angle of incidence for a ray of light at a refracting surface of a prism is $45^o$. The angle of the prism is $60^o$. If the ray suffers minimum deviation through the prism,the angle of minimum deviation and the refractive index of the material of the prism,respectively,are: