A ray of light entering from air into a denser medium of refractive index $\frac{4}{3}$, as shown in figure.
The light ray suffers total internal reflection at the adjacent surface as shown. The maximum value of angle $\theta$ should be equal to:

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 $n_1=1.2+\frac{10.8\times {10}^{-14}}{{\lambda }^2}$ 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 ____ $\mathrm{nm}.$

The angle of deviation through a prism is minimum when 

(A) Incident ray and emergent ray are symmetric to the prism

(B) The refracted ray inside the prism becomes parallel to its base

(C) Angle of incidence is equal to that of the angle of emergence

(D) When angle of emergence is double the angle of incidence

Choose the correct answer from the options given below :

A deviation of $2°$ is produced in the yellow ray when prism of crown and flint glass are achromatically combined. Taking dispersive powers of crown and flint glass are $0.02$ and $0.03$ respectively and refractive index for yellow light for these glasses are $1.5$ and $1.6$ respectively. The refracting angles for crown glass prism will be ________$°$ (in degree)

(Round off to the Nearest Integer)