White light is passed through a prism whose angle is $5^o$. If the refractive indices for rays of red and blue colour are respectively $1.64$ and $1.66$,the angle of deviation between the two colours will be.....$^o$.

The angle of minimum deviation for a prism of refractive index $1.5$ is equal to the angle of the prism. The angle of the prism is . . . . . . . $(\sin 48^{\circ} 36^{\prime} = 0.75)$

If the refractive angles of two prisms made of crown glass are $10^o$ and $20^o$ respectively,then the ratio of their angular dispersions will be

Assertion: There exist two angles of incidence for the same magnitude of deviation (except for minimum deviation) by a prism kept in air.
Reason: In a prism kept in air,a ray is incident on the first surface and emerges out of the second surface. If another ray is incident on the second surface along the path of the previous emergent ray,then this ray emerges out of the first surface along the path of the previous incident ray. This principle is called the principle of reversibility of light.

The angle of a prism is $A$. One of its refracting surfaces is silvered. Light rays falling at an angle of incidence $2A$ on the first surface return back through the same path after suffering reflection at the silvered surface. The refractive index $\mu$ of the prism is

$A$ flint glass prism and a crown glass prism are to be combined in such a way that the deviation of the mean ray is zero. The refractive indices of flint and crown glasses for the mean ray are $1.620$ and $1.518$ respectively. If the refracting angle of the flint prism is $6.0^{\circ}$,what would be the refracting angle of the crown prism (in $^{\circ}$)?