Solid State Physics MCQs Question and Answer in Engineering Physics

An extrinsic semiconductor sample of cross-section A and length L is doped in such a way that the dopping concentration varies as $${N_D}\left( x \right) = {N_0}\exp \left( { - \frac{x}{L}} \right),\,{N_0}$$      is a constant. Assume that the mobility $$\mu $$ of the majority carriers remains constant. The resistance R of the sample is given by

Consider the Atomic Packing Factor (APF) of the following crystal structures:
P. Simple cubic
Q. Body centred cubic
R. Face centred cubic
T. Hexagonal close packed
Which two of the above structures have equal APF?

If the number density of a free electron gas changes from 10²⁸ to 10²⁶ electron/m³, the value of plasma frequency (in Hz) changes from 5.7 × 10¹⁵ to

The dielectric constant of water is 80. However its refractive index is 1.75 invalidating the expression n = ε^1/2. This is because

Density of states of free electrons in a solid moving with an energy 0.1 eV is given by 2.15 × 10²¹ 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

In a cubic system with cell edge a, two phonons with wave vectors $${\overrightarrow {\bf{q}} _1}$$ and $${\overrightarrow {\bf{q}} _2}$$ collide and produce a third phonon with a wave. vector $${\overrightarrow {\bf{q}} _3}$$ such that $${\overrightarrow {\bf{q}} _1} + {\overrightarrow {\bf{q}} _2} = {\overrightarrow {\bf{q}} _3} + \overrightarrow {\bf{R}} $$    where, $$\overrightarrow {\bf{R}} $$ is a lattice vector. Such a collision process will lead to (a)

The point group symmetrics of the three molecules shown in figures are respectively

[Notation C_2v = 2 mm; C_2h = 2/m; D_2h = mmm]

The thermal conductivity of a given material reduces, when it undergoes a transition from its normal state to the superconducting state. The reason is

Silicon has diamond structure with unit cell edge a = 0.542 nm. The interatomic separation is

A metal with body centred cubic (bcc) structure shows the first (i.e. smallest angle) diffraction peak at a Bragg angle of θ = 30°. The wavelength of X-ray used is 2.1\[{{\rm{\dot A}}}\] . The volume of the primitive unit cell of the metal is