Free Dawn of Modern Physics MCQs with Answers
739 Dawn of Modern Physics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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Read the Dawn of Modern Physics notesFree MDCAT chapter notes with key terms739 questions · page 37 of 37
- A. Infinite
- B. Zero m
- C. 2 meter
- D. None of above.
Explanation: Formula for length contraction is L=L0√1−v2/c2, where: • L = new length (m) • L0 = original length (m) • v = speed of object (ms−1) • c =…
Correct answer: Zero m- A. 0.51 joule
- B. 1.02 joule
- C. 9.11 x 10^-32 joule
- D. 8.2 x 10^-14 joule
Explanation: The rest mass energy of an electron can be calculated using Einstein's equation:E = mc²E = 9.11 × 10-31 × (3 × 108)²E = 9.11 × 10-31 × 9 ×…
Correct answer: 8.2 x 10^-14 joule- A. Equal to the speed of light
- B. Greater than speed of light
- C. Comparable to the speed of light
- D. None of these
Explanation: When a charge moves at a relativistic speed, it means it is moving at a significant fraction of the speed of light, approaching but not…
Correct answer: Comparable to the speed of light- A. ionized state
- B. stimulations
- C. population inversion
- D. all of these
Explanation: GROUND STATE: The ground state of an electron, the energy level it normally occupies, is the state of lowest energy for that electron.
Correct answer: population inversion- A. photoelectric effect
- B. compton effect
- C. penetrating effect
- D. diffraction
Explanation: The wave nature of an electron is illustrated by its electron diffraction, as explained by davisson germer experiment.
Correct answer: diffraction- A. double
- B. four times
- C. six times
- D. sixteen times
Explanation: BLACK BODY: A blackbody is a theoretical or model body that absorbs all radiation falling on it, reflecting or transmitting none.
Correct answer: sixteen times- A. penetrating power of x-ray increases
- B. intensity of x-rays increases
- C. wavelength of x-rays increases
- D. all of these
Explanation: X-RAY TUBE: An X-ray tube is a vacuum tube that converts electrical input power into X-rays.
Correct answer: intensity of x-rays increases- A. Photon
- B. Roton
- C. Positron
- D. Antineutrino
Explanation: Antimatter is a type of matter made up of antiparticles. A positron is the antiparticle of an electron, making it the correct answer.
Correct answer: Positron- A. Wave-particle duality
- B. Only wave nature
- C. Only particle nature
- D. Neither wave nor particle nature
Explanation: According to debroglie , all mater particles in motion have dual nature and thus he derived an equation which is E=hc/λ
Correct answer: Wave-particle duality- A. 7.3 × 10 -34 m
- B. 1.1 × 10 -34 m
- C. 1.8 × 10 -35 m
- D. 9.9 × 10 -34 m
Explanation: λ= h/mv = 6.626 x 10-34 / 0.02 x 300 = 1.1 × 10 -34 m
Correct answer: 1.1 × 10 -34 m- A. The photoelectric effect
- B. The Compton effect
- C. The spectral radiation form cavity radiation
- D. The reflection of electrons by crystal
Explanation: By Huygens principle, reflection of electrons shows the wave nature of light. So, D is the answer.
Correct answer: The reflection of electrons by crystal- A. Line spectra of action
- B. The production of x-rays
- C. The photoelectric erect
- D. Electrons diffraction by crystalline material
Explanation: The wave properties of electrons can be demonstrated through diffraction, superposition and interference.
Correct answer: Electrons diffraction by crystalline material- 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…
Correct answer: Occur at the same co-ordinates- 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…
Correct answer: 0.02 nm- 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…
Correct answer: Time- 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…
Correct answer: A- A. Angular Momentum
- B. Work
- C. Force
- D. Torque
Explanation: The unit of planck's constant is equivalent to that of angular momentum.
Correct answer: Angular Momentum- 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.
Correct answer: Both He and Ne739. 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)…
Correct answer: Failed to explain ultraviolet region