1Which experiment historically established the particle nature of light?
A.Diffraction
B.Interference
C.Photoelectric Effect
D.Polarization
Correct Answer: Photoelectric Effect
Explanation:
Interference, diffraction, and polarization demonstrate the wave nature of light, while the Photoelectric effect demonstrates the particle (quantum) nature of light.
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2According to Planck's hypothesis, energy is emitted or absorbed in discrete packets called quanta. The energy of a quantum is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
Planck's law states that the energy of a photon is proportional to its frequency, given by , where is Planck's constant.
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3In the photoelectric effect, the minimum energy required to remove an electron from the surface of a metal is called:
A.Kinetic Energy
B.Potential Energy
C.Work Function
D.Stopping Potential
Correct Answer: Work Function
Explanation:
The Work Function () is the minimum amount of energy required by an electron to escape from a metal surface.
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4The Einstein's photoelectric equation is given by (where is maximum kinetic energy, is frequency, and is work function):
A.
B.
C.
D.
Correct Answer:
Explanation:
Einstein's photoelectric equation states that the maximum kinetic energy of the emitted electron is the difference between the photon's energy () and the work function ().
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5The de Broglie wavelength associated with a particle of momentum is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
According to the de Broglie hypothesis, the wavelength of matter waves is inversely proportional to momentum: .
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6If the velocity of a particle is doubled, its de Broglie wavelength will:
A.Become half
B.Remain the same
C.Double
D.Become four times
Correct Answer: Become half
Explanation:
Since , wavelength is inversely proportional to velocity. If doubles, becomes half.
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7The de Broglie wavelength of an electron accelerated through a potential difference of volts is approximately given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
Substituting the constants , , and into , we get .
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8Which of the following bodies will have the shortest de Broglie wavelength if they all move with the same velocity?
A.Alpha particle
B.Electron
C.Neutron
D.Proton
Correct Answer: Alpha particle
Explanation:
. For constant velocity, . The alpha particle has the largest mass among the options, so it has the shortest wavelength.
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9The de Broglie wavelength of a gas molecule at absolute temperature is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
The kinetic energy of a gas molecule is . Substituting into , we get .
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10The Heisenberg Uncertainty Principle states that the product of uncertainties in position () and momentum () is always:
A.
B.
C.
D.
Correct Answer:
Explanation:
Heisenberg's Uncertainty Principle states that it is impossible to measure both position and momentum simultaneously with arbitrary precision, with the limit .
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11Why is the wave nature of a moving cricket ball not observed in daily life?
A.Its velocity is too high
B.It does not satisfy Planck's law
C.Its mass is too large, making negligible
D.It is not a charged particle
Correct Answer: Its mass is too large, making negligible
Explanation:
Because , the large mass of macroscopic objects leads to an extremely small wavelength that is undetectable.
Correct Answer: Electrons cannot exist inside the nucleus
Explanation:
If an electron were confined to the nucleus (size m), the uncertainty in velocity would exceed the speed of light (or require impossibly high energy), which is physically impossible.
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13Another form of Heisenberg's uncertainty principle relates Energy () and Time () as:
A.
B.
C.
D.
Correct Answer:
Explanation:
The uncertainty principle also applies to the measurement of energy and the time duration of the measurement.
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14The velocity with which the envelope of a wave packet moves is called:
A.Sound velocity
B.Light velocity
C.Phase velocity
D.Group velocity
Correct Answer: Group velocity
Explanation:
The group velocity () represents the velocity of the wave packet (envelope) and corresponds to the velocity of the particle.
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15The phase velocity () is given by the relation:
A.
B.
C.
D.
Correct Answer:
Explanation:
Phase velocity is the rate at which the phase of the wave propagates in space, defined as ratio of angular frequency to wave number.
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16For a non-relativistic material particle, the relation between group velocity () and particle velocity () is:
A.
B.
C.
D.
Correct Answer:
Explanation:
The group velocity of the matter wave associated with a moving particle is equal to the classical velocity of that particle.
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17The phase velocity of matter waves associated with a particle moving with velocity is:
A.
B.Zero
C.
D.
Correct Answer:
Explanation:
Using relativity, . Since , the phase velocity .
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18In a non-dispersive medium, the relationship between phase velocity () and group velocity () is:
A.
B.
C.
D.
Correct Answer:
Explanation:
In a non-dispersive medium, velocity is independent of wavelength, so the phase velocity and group velocity are equal.
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19The wave function in quantum mechanics represents:
A.The momentum of the particle
B.The exact position of the particle
C.The probability amplitude
D.The energy of the particle
Correct Answer: The probability amplitude
Explanation:
itself has no direct physical meaning but is the probability amplitude. Its square modulus represents probability density.
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20The quantity represents:
A.Mass density
B.Probability density
C.Energy density
D.Charge density
Correct Answer: Probability density
Explanation:
According to Max Born's interpretation, (or ) represents the probability of finding the particle per unit volume (probability density).
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21For a wave function to be well-behaved, it must be:
A.Real and positive
B.Zero everywhere
C.Finite, continuous, and single-valued
D.Infinite, discontinuous, and multi-valued
Correct Answer: Finite, continuous, and single-valued
Explanation:
To be physically meaningful, must be finite (normalizable), continuous (for momentum definition), and single-valued (unique probability).
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22The normalization condition for a wave function over all space is:
A.
B.
C.
D.
Correct Answer:
Explanation:
Normalization ensures that the total probability of finding the particle somewhere in the entire universe is 1 (100%).
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23The operator for momentum () in one dimension is:
A.
B.
C.
D.
Correct Answer:
Explanation:
In quantum mechanics, the momentum operator corresponds to the spatial derivative multiplied by .
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24The operator for total energy (Hamiltonian ) in the time-independent Schrodinger equation is:
A.
B.
C.
D.
Correct Answer:
Explanation:
The Hamiltonian is the sum of Kinetic Energy operator () and Potential Energy operator ().
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25Schrodinger's time-independent wave equation in one dimension is:
A.
B.
C.
D.
Correct Answer:
Explanation:
This is the standard form derived from , where kinetic energy is expressed as a second derivative.
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26For a particle in a one-dimensional box of length with infinite potential walls, the potential inside the box () is:
A.
B.$0$
C.
D.
Correct Answer: $0$
Explanation:
The 'Particle in a Box' model assumes a free particle inside the box, meaning potential energy is zero inside and infinite outside.
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27The wave function for a particle in a 1D box of width is given by (where is an integer):
A.
B.
C.
D.
Correct Answer:
Explanation:
Solving Schrodinger's equation with boundary conditions yields sine functions normalized by .
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28The energy eigenvalues for a particle in a 1D box of length are given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
Derived from and . Using instead of , .
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29The lowest possible energy (Zero Point Energy) for a particle in a box corresponds to:
A.
B.
C.
D.
Correct Answer:
Explanation:
The quantum number cannot be zero (as would be zero everywhere), so the lowest state is .
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30Which of the following statements is true for a particle in a box?
A.Energy levels are continuous
B.Energy levels are discrete (quantized)
C.The particle can exist outside the box
D.The particle can be at rest ()
Correct Answer: Energy levels are discrete (quantized)
Explanation:
Confinement of the wave leads to standing waves, which allows only specific (discrete) energy values.
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31The spacing between energy levels for a particle in a box:
A.Varies randomly
B.Increases as increases
C.Remains constant
D.Decreases as increases
Correct Answer: Increases as increases
Explanation:
Since , the gap . The spacing increases with .
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32In the Quantum Tunneling effect, a particle can cross a potential barrier even if:
A.Its Total Energy () is less than the Barrier Height ()
B.The barrier width is infinite
C.
D.
Correct Answer: Its Total Energy () is less than the Barrier Height ()
Explanation:
Classically impossible, quantum mechanics allows a non-zero probability of finding a particle on the other side of a barrier where .
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33The probability of tunneling decreases exponentially with:
A.Increasing particle energy
B.Increasing barrier width and height
C.Decreasing barrier width
D.Decreasing particle mass
Correct Answer: Increasing barrier width and height
Explanation:
The transmission coefficient . Increasing the width or the barrier height (which increases ) drastically reduces probability.
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34Which device works on the principle of quantum tunneling?