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 18 of 37
- A. Double
- B. Half
- C. Unchanged
- D. Quarter
Explanation: When a nucleus releases gamma rays, its mass remains unchanged. Gamma rays are emitted as a result of nuclear transitions, but they do not…
Correct answer: Unchanged- A. Emits all radiation
- B. Absorbs all radiation
- C. Both A and B
- D. None of these
Explanation: A blackbody is defined as an ideal body that allows all incident radiation to pass into it (zero reflectance) and that absorbs internally…
Correct answer: Both A and B- A. Remain constant
- B. Increases
- C. Decreases
- D. None of these
Explanation: In the Compton effect, the frequency of the incident photon decreases. This occurs because when the incident photon collides with an…
Correct answer: Decreases- A. Momentum
- B. Charge
- C. Mass
- D. All of these options are correct
Explanation: Light carries momentum as every moving body, so when light energy converts to electrical energy, Momentum is conserved.
Correct answer: Momentum- A. Compton
- B. De' broglie
- C. Einstein
- D. Max planck
Explanation: The concept originated (1905) in Albert Einstein's explanation of the photoelectric effect, in which he proposed the existence of discrete…
Correct answer: Einstein- A. 900
- B. 500
- C. 1300
- D. 1600
Explanation: Correct option is C. On heating the black platinum wire, temperature increases and thus the peak wavelength decreases because of which the…
Correct answer: 1300- A. Newton's law
- B. Einstein law
- C. Coulomb law
- D. All of these options are correct
Explanation: The correct relationship between mass and energy is described by Einstein's famous equation, E=mc², where E represents energy, m…
Correct answer: Einstein law- A. Mass
- B. Velocity
- C. Kinetic energy
- D. Charge
Explanation: The wavelength of a matter wave is indeed independent of charge. The de Broglie wavelength is applicable to all particles, whether they…
Correct answer: Charge- A. Wavelength of incident light
- B. Frequency of incident light
- C. Energy of incident light
- D. Intensity of incident light
Explanation: According to Planck's quantum concept, the intensity of an incident beam (electromagnetic wave) means, the number of photons in the beam.
Correct answer: Intensity of incident light- A. Wavelength of incident light
- B. Frequency of incident light
- C. Energy of incident light
- D. Intensity of incident light
Explanation: According to Planck's quantum concept, the intensity of an incident beam (electromagnetic wave) means, the number of photons in the beam.
Correct answer: Intensity of incident light- A. Double
- B. Half
- C. Remain same
- D. Zero
Explanation: When a photon is scattered from a mirror, its momentum becomes double. This can be explained using the law of reflection, which states…
Correct answer: Double352. From the following properties of a wave, the one that is independent of the other three is its?
- A. Amplitude
- B. Frequency
- C. Wavelength
- D. Time period
Explanation: The amplitude of a wave represents its intensity or strength, and it does not depend on frequency, wavelength, or time period.
Correct answer: Amplitude- A. Photovoltaic Effect
- B. Charge
- C. Mass
- D. All of these
Explanation: Solar cells follow photovoltaic effect in which energy and momentum are conserved hence momentum is the answer.
Correct answer: Photovoltaic Effect- A. 0.01 eV s m-1
- B. 0.05 eV s m-1
- C. 0.03 eV s m-1
- D. 0.04 eV s m-1
Explanation: Energy (E) of the photon of 3 MeV = 3 x 106 eVLinear momentum of photon p = E/c, where c is the speed of light in a vacuumSo p= (3 x…
Correct answer: 0.01 eV s m-1- A. Positron & electron
- B. Photons
- C. Electron & neutron
- D. B & C are correct
Explanation: Pair production, as implied by the name, is the production of a "position and electron" pair when a photon of high energy (gamma ray)…
Correct answer: Positron & electron- A. Photoelectric effect
- B. Interference
- C. Polarization
- D. Matter waves
Explanation: The photoelectric effect occurs when light ejects electrons from a metal surface, which can only be explained if light consists of…
Correct answer: Photoelectric effect- A. Alpha
- B. Gamma
- C. Beta
- D. No Radiation can pass through it.
Explanation: A black body is an idealized physical object that absorbs all radiation that falls on it.
Correct answer: No Radiation can pass through it.- A. All frames
- B. Frame of reference
- C. Non-Inertial frame
- D. Inertial frame
Explanation: Galilean transformations apply to inertial frames of reference. These are frames of reference in which an object remains at rest or moves…
Correct answer: Inertial frame- A. fixed always
- B. not fixed always
- C. at rest
- D. none of these
Explanation: Option B is correct since there can be two frames of reference and they are not fixed Option A is incorrect since the frames of reference…
Correct answer: not fixed always- A. 1
- B. less than 1
- C. Absolutely no
- D. None of these
Explanation: In the subatomic world, predictions are made with less than-perfect precision due to the uncertainty principle in quantum mechanics.
Correct answer: less than 1