The cross-section of a prism $(\mu = 1.5)$ is an equilateral triangle. $A$ ray of light is incident perpendicular on one of the faces. The angle of deviation of the ray is......$^o$

For an equilateral prism,it is observed that when a ray strikes grazingly at one face,it emerges grazingly at the other. Its refractive index will be

$A$ prism of a certain angle deviates the red and blue rays by $8^{\circ}$ and $12^{\circ}$ respectively. Another prism of the same angle deviates the red and blue rays by $10^{\circ}$ and $14^{\circ}$ respectively. The prisms are small-angled and made of different materials. The dispersive powers of the materials of the prisms are in the ratio:

$A$ prism has a refracting angle '$A$'. The second refracting surface of the prism is silvered. $A$ light ray falling on the first refracting surface with an angle of incidence '$2A$' reaches the second surface and returns back through the same path due to reflection at the silvered surface. The refractive index of the material of the prism is:

Three prisms $1, 2,$ and $3$ have a prism angle $A = 60^{\circ}$. Their refractive indices are $1.4, 1.5,$ and $1.6$ respectively. If $\delta_1, \delta_2,$ and $\delta_3$ are their angles of deviation,then:

$A$ prism of angle $A=1^{\circ}$ has a refractive index $\mu=1.5$. $A$ good estimate for the minimum angle of deviation (in degrees) is close to $N/10$. The value of $N$ is......