(i) For a glass prism (

(i) Explain briefly the process of emission of light by a Light Emitting Diode (LED).
(ii) Which semiconductors are preferred to make LEDs and why?
(iii) Give two advantages of using LEDs over conventional incandescent lamps.

A capacitor of unknown capacitance, a resistor of 100 V and an inductor of self-inductance L5(4/p²) henry are connected in series to an ac source of 200V and 50 Hz. Calculate the value of the capacitance and impedance of the circuit when the current is in phase with the voltage. Calculate the power dissipated in the circuit.

Plot a graph showing the variation of binding energy per nucleon as a function of mass number. Which property of nuclear force explains the approximate constancy of binding energy in the range 30 < A < 170? How does one explain the release of energy in both the processes of nuclear fission and fusion from the graph?