Draw a graph showing the variation of potential energy of a pair of nucleons as a function of their separation. Indicate the region in which the nuclear force is (a) attractive and (b) repulsive.

(a) How will the De Broglie wavelength associated with an electron be affected when the (i) velocity of the electron decreases ? and (ii) accelerating potential is increased? Justify your answer.

OR

(b) How would the stopping potential for a given photosensitive surface change if (i) the frequency of the incident radiation were increased? and (ii) the intensity of incident radiation were decreased? Justify your answer.

Identify the electromagnetic wave whose wavelengths range is from about

(a) $$10^{-12} \mathrm{~m}$$ to about $$10^{-8} \mathrm{~m}$$.

(b) $$10^{-3} \mathrm{~m}$$ to about $$10^{-1} \mathrm{~m}$$.

Write one use of each.

Depict the orientation of an electric dipole in (a) stable and (b) unstable equilibrium in an external uniform electric field. Write the potential energy of the dipole in each case.