Differentiate between amplitude modulated (AM) and frequency modulated (FM) waves by drawing suitable diagrams. Why is FM signal preferred over AM signal?

When the electron orbiting in hydrogen atom in its ground state moves to the third excited state, show how the de Broglie wavelength associated with it would be affected.

Define a wave-front. Using Huygens’ principle, draw the shape of a refracted wave-front, when a plane wave is incident on a convex lens.

OR

(a) When a wave is propagating from a rarer to a denser medium, which characteristic of the wave does not change and why? (b) What is the ratio of the velocity of the wave in the two media of refractive indices μ₁ and μ₂?

Determine the distance of closest approach when an alpha particle of kinetic energy 4 �5 MeV strikes a nucleus of Z = 80, stops and reverses its direction.

Deduce the expression for the torque acting on a planar loop of area and carrying current I placed in a uniform magnetic field . If the loop is free to rotate, what would be its orientation in stable equilibrium?