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.

(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.

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.’

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?

A metal rod of square cross-sectional area A having length l has current I flowing through it when a potential difference of V volt is applied across its ends (figure I). Now the rod is cut parallel to its length into two identical pieces and joined as shown in figure II. What potential difference must be maintained across the length 2l so that the current in the rod is still I?