The refractive index of an equilateral prism is $$\sqrt 2 $$. The angle of emergence under minimum deviation position of prism, in degree, is ___________.

A parallel beam of light is allowed to fall on a transparent spherical globe of diameter 30 cm and refractive index 1.5. The distance from the centre of the globe at which the beam of light can converge is _____________ mm.

A small bulb is placed at the bottom of a tank containing water to a depth of $$\sqrt7$$ m. The refractive index of water is $${4 \over 3}$$. The area of the surface of water through which light from the bulb can emerge out is x$$\pi$$ m². The value of x is __________.

A light ray is incident, at an incident angle $$\theta$$₁, on the system of tow plane mirrors M₁ and M₂ having an inclination angle 75$$^\circ$$ between them (as shown in figure). After reflecting from mirror M₁ it gets reflected back by the mirror M₂ with an angle of reflection 30$$^\circ$$. The total deviation of the ray will be _____________ degree.