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

The angle of minimum deviation produced by a thin prism in air is $\delta_1$. If it is immersed in water,the angle of minimum deviation is $\left[_{a}\mu_{g}=\frac{3}{2}, _{a}\mu_{w}=\frac{4}{3}\right]$.

$A$ given ray of light suffers minimum deviation in an equilateral prism $P$. Additional prisms $Q$ and $R$ of identical shape and material are now added to $P$ as shown in the figure. The ray will suffer

For a thin prism,if the angle of prism is $4^{\circ}$ and the refractive index is $1.6$,then the angle of minimum deviation will be . . . . . . . (in $^{\circ}$)

$A$ 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 $\left[\sin \frac{\pi}{6}=0.5\right]$

$A$ combination of two prisms,one of flint glass and the other of crown glass,produces dispersion without deviation. The angle of the flint glass prism is $15^\circ$. The net angular dispersion for red and violet light will be ..... (Given: for crown glass $\mu = 1.52, \omega = 0.02$; for flint glass $\mu = 1.65, \omega = 0.03$). (in $^\circ$)