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 10 of 37
- A. 10-11
- B. 10-8
- C. 10-3
- D. 10+3
Explanation: In the context of population inversion in a Ruby laser, the correct answer is that atoms can reside in the excited state for a relatively…
Correct answer: 10-3- A. Light amplification by stimulated emission of radiation
- B. Light annihilation by stimulated emission of radiation
- C. Light amplitude of stimulated emission of radiation
- D. Light amplification by stimulated emission of radio
Explanation: Light amplification by stimulated emission of radiation
Correct answer: Light amplification by stimulated emission of radiation- A. It consists of one ray of light
- B. It consists of one wavelength
- C. It consists of carbon monoxide gas
- D. It consists of photons having 1 eV energy
Explanation: Monochromatic light refers to light that has only one wavelength or frequency.
Correct answer: It consists of one wavelength- A. Visible spectrum
- B. X rays
- C. Radio waves
- D. Infrared waves
Explanation: We know that X-rays are produced due to transition of electron from higher shell yo lower shell , producing continuous and characteristic…
Correct answer: X rays- A. Visible
- B. Ultraviolet
- C. Infrared
- D. X-rays
Explanation: Electromagnetic radiation comes in a range of energies, known as the electromagnetic spectrum.
Correct answer: Infrared186. Davisson and Germer proved experimentally the wave nature of particles under the phenomenon of:
- A. Reflection
- B. Refraction
- C. Interference
- D. Diffraction
Explanation: In the Davisson-Germer experiment, electrons were scattered off of a nickel crystal.
Correct answer: Diffraction- A. Less uncertainty
- B. High uncertainty
- C. High accuracy
- D. Equal uncertainty
Explanation: The uncertainty principle states that the uncertainty in the position of a particle and the uncertainty in its momentum must always be…
Correct answer: High uncertainty- A. Newton's theory
- B. Einstein's theory
- C. Hertz theory
- D. Special theory of relativity
Explanation: An inertial frame of reference is one that satisfies the following conditions: It is not accelerating. It is not rotating.
Correct answer: Newton's theory- A. Decreased
- B. Increased
- C. Remain same
- D. Maximum
Explanation: The speed of light received by the observer will remain the same, regardless of the motion of the light source.
Correct answer: Remain same- A. Remain same
- B. Decreased
- C. Increased
- D. Doubled
Explanation: The relativistic length of a moving object will be decreased, as seen by an observer moving relative to the object.
Correct answer: Decreased- A. Equal to speed light
- B. Less than the speed of light
- C. Greater than the speed of light
- D. Not comparable with speed of light
Explanation: If the rest mass of a particle is zero, then its speed is the speed of light.
Correct answer: Equal to speed light- A. Pressure
- B. Volume
- C. Temperature
- D. Density
Explanation: Blackbody radiation depends only on the temperature of the object. This is because a blackbody is an ideal absorber and emitter of…
Correct answer: Temperature193. If the temperature of the black body is doubled then the emitted energy from it will be increased:
- A. Doubled
- B. Four times
- C. Eight times
- D. Sixteen times
Explanation: If the temperature of a blackbody is doubled, then the emitted energy from it will be increased by a factor of 16.
Correct answer: Sixteen times- A. Cavity
- B. Radiator
- C. Source of radiation
- D. None of them
Explanation: A perfect absorber must also be a perfect radiator according to the principle of reciprocity.
Correct answer: Radiator- A. Electrons have a wave nature
- B. Electrons can be focused by an electric field
- C. Electrons can be focused by a magnetic field
- D. All of the above
Explanation: To summarize, electron microscopes utilize the wave nature of electrons, employ electric fields for focusing, and also use magnetic fields…
Correct answer: All of the above- A. Length contraction
- B. Space-time transformation
- C. Time dilation
- D. Mass variation
Explanation: Option B is not the result of the special theory of relativity. While space-time transformation is a concept that is used in the theory of…
Correct answer: Space-time transformation- A. 1.6 × 10^15 Hz
- B. 1.6 × 10^12 Hz
- C. 6.63 × 10^-34 Hz
- D. 1.6 × 10^-19 Hz
Explanation: The work function (W) is the minimum energy required to remove an electron from the surface of a metal.
Correct answer: 1.6 × 10^15 Hz- A. [MLT-2]
- B. [ML2T-1]
- C. [MLT-3]
- D. [ML2T-2]
Explanation: Using the SI units for energy (J) and frequency (Hz), the equation is written as:[h] = [E] / [f][h] = [J] / [Hz] Since 1Hz is equivalent…
Correct answer: [ML2T-1]- A. Energy
- B. Work
- C. Linear momentum
- D. Angular momentum
Explanation: The dimension of angular momentum is M1L2T-1. This option is correct oneAngular momentum has the formula as π π L = nh / 2 π ,where is the…
Correct answer: Angular momentum- A. Kgms-2
- B. Nms-2
- C. Kgm2s-2
- D. Both B and C
Explanation: E=mc²Where E is energy, m is mass and c is the speed of light, the unit of mass is kg and the unit of speed is m/s…
Correct answer: Kgm2s-2