An achromatic prism is made by combining two prisms $P_1$ $(\mu_v = 1.523, \mu_r = 1.515)$ and $P_2$ $(\mu'_v = 1.666, \mu'_r = 1.650)$,where $\mu$ represents the refractive index. If the angle of the prism $P_1$ is $10^o$,then the angle of the prism $P_2$ will be.....$^o$

The ratio of the angle of minimum deviation of a prism in air to that when it is dipped in water is (given $_a\mu_g = 3/2$ and $_a\mu_w = 4/3$).

$A$ prism of refractive index $n_{1}$ and another prism of refractive index $n_{2}$ are stuck together (as shown in the figure). $n_{1}$ and $n_{2}$ depend on $\lambda$, the wavelength of light, according to the relation:
${n}_{1}=1.2+\frac{10.8 \times 10^{-14}}{\lambda^{2}} \text{ and } {n}_{2}=1.45+\frac{1.8 \times 10^{-14}}{\lambda^{2}}$
The wavelength for which rays incident at any angle on the interface $BC$ pass through without bending at that interface will be $....\,nm.$

$A$ triangular prism of glass is shown in the figure. $A$ ray incident normally to one face is totally reflected,if $\theta = 45^o$. The index of refraction of glass is

$A$ thin prism $P_1$ with an angle $6^{\circ}$ and made of glass of refractive index $1.54$ is combined with another prism $P_2$ made from glass of refractive index $1.72$ to produce dispersion without average deviation. The angle of prism $P_2$ is $........{}^{\circ}$

Three prisms of crown glass,each having a prism angle of $9^o$,and two prisms of flint glass are used to make a direct vision spectroscope. What will be the angle of the flint glass prisms in degrees if the refractive index $\mu$ for flint glass is $1.60$ and $\mu$ for crown glass is $1.53$ (in $^o$)?