$A$ thin prism $P_1$ with angle $6^o$ and made from glass of refractive index $1.54$ is combined with another thin prism $P_2$ of refractive index $1.72$ to produce dispersion without deviation. The angle of prism $P_2$ will be:

$A$ light ray incident normally on one face of an equilateral prism and emerges out grazingly at the other face. The refractive index of the prism is

The refractive index of a transparent liquid filled in an equilateral hollow prism is $\sqrt{2}$. The angle of minimum deviation for the liquid will be (in $^{\circ}$)

If $r_1$ and $r_2$ are the angles of refraction at the first and second faces of a prism,respectively,then the angle of the prism is:

$A$ prism having refractive index $\sqrt{2}$ and refracting angle $30^{\circ}$ has one of the refracting surfaces silvered. The beam of light incident on the other refracting surface will retrace its path,if the angle of incidence is $\left[\sin \frac{\pi}{6}=0.5\right]$

The angle of deviation produced by a thin prism when placed in air is $\delta_1$ and that when immersed in water is $\delta_2$. The refractive indices of glass and water are $\frac{3}{2}$ and $\frac{4}{3}$ respectively. The ratio $\delta_1 : \delta_2$ is