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Free Quantum Theory and Radiation MCQs with Answers

147 Quantum Theory and Radiation MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Quantum theory treats electromagnetic radiation as packets of energy called photons, with energy proportional to frequency through E equals hf. The topic covers Planck's hypothesis, photon momentum, the photoelectric effect, threshold frequency, work function and wave particle duality, distinguishing quantised energy exchange from classical continuous radiation.

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147 questions · page 8 of 8

141. The proper time between two events is measured by a clock at rest in a reference frame in which the two events:

  • A. Occurs at the same time
  • B. Occur at the same co-ordinates
  • C. Are separated by the distance a light signal can travel during the time interval
  • D. Satisfy none of the above

Explanation: The proper time interval between two events is the amount of elapsed time reckoned on the clock of an observer in an inertial frame of…

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Correct answer: Occur at the same co-ordinates

142. If 50 KV is the applied potential in ax X-ray tube then the minimum wavelength of X-rays produced is:

  • A. 0.2 nm
  • B. 2 nm
  • C. 0.02 nm
  • D. 2 Å

Explanation: To find the minimum wavelength of X-rays produced in an X-ray tube, we use the formula: 𝝺min = hc/qeV, where:h is Planck's constant…

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Correct answer: 0.02 nm

143. In Einstein's universe what is the fourth dimension:

  • A. Distance
  • B. Speed
  • C. Time
  • D. Energy

Explanation: Einstein's theory of relativity introduced the revolutionary concept of spacetime, where the three dimensions of space are intertwined…

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Correct answer: Time

144. An electron has charge (e) and mass (m). A proton has charge e and mass 1840m. A "Proton volt" is equal to:

  • A. A
  • B. B
  • C. C
  • D. D

Explanation: The problem defines a "Proton volt" as the energy gained by a proton (charge qp =+e) when it moves through an electric potential…

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Correct answer: A

145. The units of planks constant are the same as that of :

  • A. Angular Momentum
  • B. Work
  • C. Force
  • D. Torque

Explanation: The unit of planck's constant is equivalent to that of angular momentum.

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Correct answer: Angular Momentum

146. In He - Ne Iaser, the active material is:

  • A. He only
  • B. Ne only
  • C. Both He and Ne
  • D. None of the above

Explanation: In a He-Ne laser, the active material is a mixture of helium (He) and neon (Ne) gases.

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Correct answer: Both He and Ne

147. Raleigh Jean predicted behavior of black body radiations, this predictions came to conclusion that:

  • A. Explained with quantum theory
  • B. Explained well by mathematical treatment
  • C. Failed to explain ultraviolet region
  • D. Used Einstein's theory of relativity

Explanation: Raleigh-Jean did make predictions about black body radiation, but those predictions couldn't explain the behavior in the ultraviolet (UV)…

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Correct answer: Failed to explain ultraviolet region
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