Solid State Physics - Study Mode
[#11] If the number density of a free electron gas changes from 10 28 to 10 26 electron/m 3 , the value of plasma frequency (in Hz) changes from 5.7 × 10 15 to
Correct Answer
(B) 5.7 × 10 14
[#12] The dielectric constant of water is 80. However its refractive index is 1.75 invalidating the expression n = ε 1/2 . This is because
Correct Answer
(A) the water molecule has a permanent dipole moment
[#13] Density of states of free electrons in a solid moving with an energy 0.1 eV is given by 2.15 × 10 21 e/V cm -3 . The density of states (in e/V cm -3 ) for electrons moving with an energy of 0.4 eV will be
Correct Answer
(D) 4.30 × 10 21
[#14] In a cubic system with cell edge a, two phonons with wave vectors $${overrightarrow {x08f{q}} _1}$$ and $${overrightarrow {x08f{q}} _2}$$ collide and produce a third phonon with a wave. vector $${overrightarrow {x08f{q}} _3}$$ such that $${overrightarrow {x08f{q}} _1} + {overrightarrow {x08f{q}} _2} = {overrightarrow {x08f{q}} _3} + overrightarrow {x08f{R}} $$ xa0 xa0where, $$overrightarrow {x08f{R}} $$ is a lattice vector. Such a collision process will lead to
(a)
Correct Answer
(A) finite thermal resistance
[#15] The thermal conductivity of a given material reduces, when it undergoes a transition from its normal state to the superconducting state. The reason is
Correct Answer
(A) the cooper pairs cannot transfer energy to the lattice