A variable resistor R is connected across a cell of emf ε and internal resistance r as shown in the figure. Draw a plot showing the variation of (i) terminal voltage V and (ii) the current I, as a function of R.

When light travels from an optically denser medium to a rarer medium, why does the critical angle of incidence depend on the color of light?

What is the function of a band pass filter used in a modulator for obtaining 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?