Atom questions

3. A material has an effectively full valence band and an empty conduction band. Explain why that if these two bands overlap the material behaves as a metal and if they are separated by a few electron volts in energy the material is an insulator. 4. Calculate the minimum energy a photon must have to produce an electron hole pair in an extrinsic semiconductor of band gap 1.0 electron volts.

The temperature of the sea bed 60 m below the surface and at the surface are both 20C...

12. The temperature of the sea bed 60 m below the surface and at the surface are both 20C. A rubber balloon is inflated at the sea bed with 2.0 mole gas neglecting the works done on the rubber determine: i)the volume of the balloon at the sea bed and ii) the volume of the balloon after it has been allowed to float slowly up to the surface. ii) the volume of the balloon after it has been allowed to float slowly up to the surface

One mole of ARGON gas inside a cylinder...

2. One mole of ARGON gas inside a cylinder fitted with a piston is made to expand very slowly in good thermal contact with its surroundings. During this expansion the volume was doubled and the temperature was constant. The same expansion is performed very rapidly with the cylinder being thermal isolated. The conditions were controlled such that again the volume doubled and the temperature remained constant. Compare the pressure before and after expansion in the two cases

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 a... click for more

Electron questions

1. Explain how the degree of filling of an electron level in an isolated atom of molecule affects whether the resulting solid is an insulator, semi-conductor or metal. 2. Hence or otherwise compare the expected electrical conductivity of solid hydrogen with solid helium.