Question set

1)Which of following energies indicates the order of magnitude of the band gap in between the conduction and valence bands in a semi-conductor:

    a) 10^2 electron volts       b) 0.7 electron volts      c) 10^-8 volts



2)How many degrees of freedom does a point atom have:


a) 15     b) 4    c) 3    d) 1

4)A piston 2.0 kg of gas. Very slowly 0.5 kgm of the gas is allowed to escape.                    Determine the ratio of the pressure before and after the gas loss.




5)Why a 3 level lasing system must be pumped with light at a higher frequency than the coherent light emitted by the laser.


6)A lung contains 0.25 kg of gas. A further 0.25 kg of the gas is added at constant temperature. Assuming that the volume of the lung does not change, does the pressure in lung

a) Double       b) halve     c) remain constant


7)Microwave energy is mainly absorbed in water by


a) Domain formation b) dipole rotation c) free electron motion d) ionic      polarisation