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 31 of 37
- A. East
- B. West
- C. North
- D. South
Explanation: To determine the final direction the rat is facing, follow these steps:The rat starts by running 20' East.It turns right (now facing…
Correct answer: North- A. A. If statement I is the cause and statement II is its effect;
- B. B. If statement II is the cause and statement I is its effect;
- C. C. If both the statements I and II are independent causes;
- D. D. If both the statements I and II are effects of independent causes;
- E. E. If both the statements I and II are effects of some common cause;
Explanation: Statement II describes that many partners have withdrawn money from the society fund, likely leading to a financial shortfall.
Correct answer: B. If statement II is the cause and statement I is its effect;- A. If only I follows
- B. If only II follows
- C. If either I or II follows
- D. If neither I nor II follows
- E. If both I and II follow
Explanation: The correct course of action is to repair the road (Option A). The statement highlights the poor condition of NH-5 due to heavy…
Correct answer: If only I follows604. Photon A has twice the energy of photon B. What is the ratio of the momentum of A to that of B?
- A. 4:1
- B. 2:1
- C. 1:1
- D. 1:2
Explanation: The momentum ( P ) of a photon is directly proportional to its energy ( E ), as given by the equation P = E.c where ( c ) is the speed of…
Correct answer: 2:1- A. Electron
- B. Proton
- C. Neutron
- D. a- particle
Explanation: The particle with the shortest wavelength, when all particles have the same velocity, is the one with the highest mass.
Correct answer: a- particle- A. Photoelectric effect
- B. Compton effect
- C. Pair Production
- D. Diffraction
Explanation: The phenomenon that does not verify the particle nature of light is diffraction.
Correct answer: Diffraction607. The maximum kinetic energy of emitted photoelectrons, from different metal surfaces, depends upon:
- A. Intensity of incident light only
- B. Frequency of the incident light only
- C. Nature of metal surface
- D. Both frequency of incident light and nature of metal surface
Explanation: The maximum kinetic energy of emitted photoelectrons depends on both the frequency of the incident light and the nature of the metal…
Correct answer: Both frequency of incident light and nature of metal surface- A. Infinite
- B. Zero
- C. 1.6 x 10^-27 kg
- D. 3 x 10^8 kg
Explanation: The rest mass of a photon is 0. This is because photons are particles of light and they always move at the speed of light in a vacuum.
Correct answer: Zero- A. 1.02 MeV
- B. 1.51 MeV
- C. 0.52MeV
- D. 0.051MeV
Explanation: The minimum energy required by a photon to create an electron-positron pair is equal to 1.02 MeV . This process is known as pair production,
Correct answer: 1.02 MeV- A. 90⁰
- B. 180⁰
- C. 0⁰
- D. 45⁰
Explanation: Here is the explanation of the correct optionλ = (1-cosθ) (use substitute technique)θ = 180λ = 2h/mc
Correct answer: 180⁰- A. 4.2 eV
- B. 2.1 eV
- C. 1.2 eV
- D. 0.98 eV
Explanation: The energy of a photon can be calculated using the formula E = hc/λ, where h is Planck's constant (4.135667696 × 10-15 eV·s), c is the…
Correct answer: 2.1 eV- A. Pair production
- B. Pair annihilation
- C. Compton's effect
- D. Photoelectric effect
Explanation: B) Pair annihilation: This process occurs when a particle and its antiparticle (like an electron and a positron) collide and convert their…
Correct answer: Pair annihilation- A. same for all types of materials.
- B. different for same types of materials.
- C. less than zero for all types of materials.
- D. different for different types of materials.
Explanation: The threshold frequency (\(f_{0}\)) is the minimum frequency of incident light required to cause the emission of electrons from a metal…
Correct answer: different for different types of materials.- A. dual nature.
- B. wave nature only.
- C. particle nature only.
- D. electromagnetic nature.
Explanation: The photoelectric effect and the Compton effect both provide strong evidence that light possesses a dual nature (A).
Correct answer: dual nature.- A. Velocity
- B. Intensity
- C. Frequency
- D. Wavelength
Explanation: In the photoelectric effect, electrons are emitted from a metal surface when the frequency of the incident light exceeds a certain…
Correct answer: Frequency616. In the photoelectric effect, the maximum kinetic energy of the emitted photoelectrons depends on the
- A. saturation region.
- B. intensity of the incident light.
- C. frequency of the incident light.
- D. surface temperature of the metal surface.
Explanation: In the photoelectric effect, the maximum kinetic energy of the emitted photoelectrons depends on the frequency of the incident light.
Correct answer: frequency of the incident light.- A. Pair production.
- B. Compton's effect.
- C. Photoelectric effect.
- D. Annihilation of matter.
Explanation: The correct answer is 'Pair production.' This phenomenon occurs when a high-energy photon interacts with a nucleus and transforms into an…
Correct answer: Pair production.- A. I only.
- B. II only.
- C. I and III.
- D. II and III.
Explanation: Compton's experiment is a pivotal demonstration of the particle nature of light.
Correct answer: II only.- A. value of potential difference
- B. velocity of the emitted electrons
- C. kinetic energy of the emitted electrons
- D. number of electrons emitted per second
Explanation: When light with higher intensity falls on a metal surface, more electrons are ejected from the surface, leading to an increase in the…
Correct answer: number of electrons emitted per second- A. Has shiny surface.
- B. Has low work function.
- C. Has high threshold energy.
- D. Is sensitive to the frequency of light.
Explanation: The most suitable metal for photoelectric emission is characterized by a low work function.
Correct answer: Has low work function.