When a glass prism of refracting angle $60^{\circ}$ is immersed in a liquid, its angle of minimum deviation is $30^{\circ}$. The critical angle of glass with respect to the liquid medium is (in $^{\circ}$)

Which of the following prisms is used to see the infrared spectrum of light?

$A$ ray of light is incident normally on the first refracting face of a prism of refracting angle $A$. The ray of light comes out at grazing emergence. If one half of the prism (shaded portion) is knocked off,the same ray will:

$A$ ray of light is incident on the first face of an equilateral glass prism at an angle of incidence '$i$'. The emergent ray just grazes along the adjacent face. The refractive index of the prism is $\sqrt{2}$. The value of the angle of incidence at the first face is $(\sin 45^{\circ} = 1/\sqrt{2}, \sin 90^{\circ} = 1)$.

When a ray of light is incident normally on one refracting surface of an equilateral prism (Refractive index of the material of the prism $= 1.5$),what happens to the ray at the second refracting surface?

$A$ thin prism $P_1$ with angle $6^{\circ}$ 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