If a ray of light passes through an equilateral prism such that the angle of incidence and the angle of emergence are both equal to $70 \%$ of the angle of the prism, then the angle of minimum deviation is

An empty tank has concave murror as its bottom. When sunlight falls normally on the mirror, it is focussed $\mathrm{a}_2$ height of 32 cm from the mirror. If the tank is filled with water upto a height of 20 cm , then the sunlight focusses at (refractive index of water $=\frac{4}{3}$ )