GATE Physics: Questions 68 - 71 of 622

Get 1 year subscription: Access detailed explanations (illustrated with images and videos) to 622 questions. Access all new questions we will add tracking exam-pattern and syllabus changes. View Sample Explanation or View Features.

Rs. 350.00 or

Question number: 68

» Solid State Physics » Lattice Vibrations and Thermal Properties of Solid

Appeared in Year: 2015

Short Answer Question▾

Write in Short

The dispersion relation for phonons in a one dimensional monatomic Bravais lattice with lattice spacing Equation and consisting of ions of masses M is given by,

Equation

Where Equation is the frequency of oscillation, Equation is the wavevector and C is the spring constant. For the long wavelength modes Equation , the ratio of the phase velocity to the group velocity is ________.

Question number: 69

» Electronics » Field Effect Transistors

Appeared in Year: 2015

Short Answer Question▾

Write in Short

In the given circuit, the voltage across the source resistor is 1 V. The drain voltage (in V) is ________.

A circuit diagram consist of JFET

A Circuit Diagram Consist of JFET

Figure shows a circuit consists of three resistors and a JFET, the voltage across the source resistor is 1 V.

Question number: 70

» Thermodynamics and Statistical Physics » Black-Body Radiation and Planck's Distribution Law

Appeared in Year: 2015

MCQ▾

Question

For a black body radiation in a cavity, photons are created and annihilated freely as a result of emission and absorption by the walls of the cavity. This is because –

Choices

Choice (4) Response

a.

Photons are spin – 1 particle

b.

The chemical potential of the photons is zero

c.

Photons obey Pauli exclusion principle

d.

The entropy of the photons is very large.

Question number: 71

» Atomic and Molecular Physics » Zeeman and Stark Effects

Appeared in Year: 2015

Short Answer Question▾

Write in Short

The number of permitted transitions from Equation in the present of a weak magnetic field is ________.

f Page
Sign In