List of top Geophysics Questions asked in Common University Entrance Test

Which statements are correct for a P–N junction diode?
(A) For forward bias, P-side is connected to the positive terminal and N-side to the negative terminal of the battery.
(B) For forward bias, P-side is connected to the negative terminal and N-side to the positive terminal.
(C) For reverse bias, P-side is connected to the negative terminal and N-side to the positive terminal.
(D) For reverse bias, P-side is connected to the positive terminal and N-side to the negative terminal.
Choose the correct answer from the options given below:

In an LCR circuit, the current and emf differ in phase by $\Phi$. The value of $\Phi$ is:

In the case of a rolling solid sphere on an inclined plane making an angle of $30^\circ$ with the horizontal plane, the acceleration of the sphere rolling down the plane is (where acceleration due to gravity is $9.8 \, \text{m/s}^2$):

Consider a silicon p-n junction at $T = 300 \, \text{K}$ with doping concentrations of acceptor $N_A = 10^{16} \, \text{cm}^{-3}$ and donor $N_D = 10^{15} \, \text{cm}^{-3}$. Assume that intrinsic concentration $n_i = 1.5 \times 10^{10} \, \text{cm}^{-3}$, relative permittivity $= 11.7$, and $V_{bi} = 0.635 \, \text{V}$. The width of the space charge region in the p-n junction is:

	LIST I		LIST II
A.	Bipolar npn transistor operate in the cut-off mode.		I. The base-emitter is reverse biased and
B.	Bipolar npn transistor operate in the saturation mode.		II. Both the base-emitter and base
C.	Bipolar npn transistor operate in the inverse active mode.		III. The base-emitter is forward biased
D.	Bipolar npn transistor operate in the forward active mode.		IV. Both the base-emitter and bas

Choose the correct answer from the options given below:

	LIST I		LIST II
A.	∇ ⋅ E = ρ/ε₀		I. Gauss's Law in magnetostatics
B.	∇ ⋅ B = 0		II. Faraday's Law of electromagnetic Induction
C.	∇ × E = - ∂B/∂t		III. Gauss's Law in electrostatics
D.	∇ × B = μ₀J + μ₀ε₀ ∂E/∂t		IV. Modified Ampere's Law

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Which of the following statements are true for ideal PN junction current voltage relationship?
(A) The abrupt depletion layer approximation applies.
(B) The Maxwell-Boltzmann approximation applies to carrier statistics.
(C) The concept of low injection applies.
(D) The total current is not constant throughout the entire pn structure.
Choose the correct answer from the options given below:

Displacement current is not a conventional current but it is:

	LIST I		LIST II
A.	Intrinsic semiconductor		I. Used as a rectifier circuit
B.	N-Type Semiconductor		II. Pure form of Semiconductor
C.	P-Type Semiconductor		III. Doping of pentavalent impurity in semiconductor
D.	P-N Junction diode		IV. Doping of trivalent impurity in semiconductor

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Find the amplitude of the electric field in a parallel beam of light of intensity $2.0 \, \text{W/m}^2$:

The efficiency of Carnot’s engine working between the steam point and the ice point is:

Match List I with List II:

List I	List II
(A) (∂S/∂P)T	(I) (∂P/∂T)V
(B) (∂T/∂V)S	(II) (∂V/∂S)P
(C) (∂T/∂P)S	(III) -(∂V/∂T)P
(D) (∂S/∂V)T	(IV) -(∂P/∂S)V

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Which of the following is true for a reversible process

If the radiation emitted by a star has a maximum intensity at a wavelength of 446 nm, its surface temperature is approximately:

Which of the following statements are true for Compton effect?
(A) The wavelength of the scattered X-rays is larger than that of the incident X-rays.
(B) The change in wavelength depends on the intensity of the incident X-rays.
(C) The change in wavelength depends on the scattering angle.
(D) The wavelength of the scattered X-rays is smaller than that of the incident X-rays
Choose the correct answer from the options given below

Clausius-Clapeyron’s latent heat equation is represented as:

X-ray of wavelength 10.0 pm are scattered from a target in a Compton exper iment. If the X-rays are scattered through \(45\degree\), the scattered wavelength is

Which of the following statements are correct for the Second Law of Thermodynamics?
(A) It is impossible to derive a continuous supply of energy from a body by cooling it below the temperature of its surroundings.
(B) It is possible to derive a continuous supply of energy from a body by cooling it below the temperature of its surroundings.
(C) It is impossible for a self-acting machine, unaided by any external agency, to convey heat from a body at lower temperature to another body at higher temperature.
(D) It is possible for a self-acting machine, unaided by any external agency, to convey heat from a body at lower temperature to another body at higher temperature.
Choose the correct answer from the options given below:

10g of water at \(100\degree C \)is converted into steam at the same temperature. If the latent heat of steam is 540cal/g, the change in entropy is

Higher-energy photons are scattered from electrons initially at rest. Assume the photons are backscattered ($\theta = 180^\circ$) and their energies are much higher than the electron's rest mass energy. The wavelength shift will be \[ \frac{h}{m_e c} = 2.43 \times 10^{-12} \, \text{m}: \]

If the resonance frequency of an acoustic system is 300Hz and the half-power frequencies are 150Hz and 450Hz, the quality factor is:

Brewster's law can be expressed as:

The inter-molecular distance between two atoms of a hydrogen molecule is $0.77 \, \text{\AA}$, and the mass of a proton is $1.67 \times 10^{-27} \, \text{Kg}$. The moment of inertia of a molecule is:

Consider phosphorus doping in silicon, for $T = 300 \, \text{K}$, at concentration $N_d = 10^{16} \, \text{cm}^{-3}$. The fraction of total electrons still in the donor states is: