A device X used in communication system can convert one form of energy into another. Name the device X. Explain the function of a repeater in a communication system.’

Define Electric Flux. Write its SI unit.

(i) State Bohr postulate of hydrogen atom that gives the relationship for the frequency of emitted photon in a transition.

(ii) An electron jumps from fourth to first orbit in an atom. How many maximum number of spectral lines can be emitted by the atom? To which series these lines correspond?

OR

Use de-Broglie’s hypothesis to write the relation for the nth radius of Bohr orbit in terms of Bohr’s quantization condition of orbital angular momentum.

The wavelength λ of a photon and the de-Broglie wavelength of an electron have the same value. Show that energy of a photon is (2λmc/h) times the kinetic energy of electron; where m, c and h have their usual meaning.

Distinguish between polarized and unpolarised light. Does the intensity of polarized light emitted by a polaroid depend on its orientation? Explain briefly.

The vibrations in a beam of polarized light make an angle of 60° with the axis of the polaroid sheet. What percentage of light is transmitted through the sheet?