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.
Last updated
Read the Dawn of Modern Physics notesFree MDCAT chapter notes with key terms739 questions · page 15 of 37
281. When an observer moves with velocity of light, relative to a timing device at rest, he would notice:
- A. Absolute time
- B. Improper time
- C. Infinite time
- D. Proper time
Explanation: According to special relativity, we observe that, with regards to the timing device at rest, the observer, in motion, would experience a…
Correct answer: Improper time- A. Δλ = h/m0c (1 + cosθ)
- B. Δλ = h/m0c (1 + cos2θ)
- C. Δλ = h/m0c (1 - cosθ)
- D. Δλ = h/m0c2 (1 + cosθ)
Explanation: The correct answer is Option C: Δλ = h/m0c (1 - cosθ). This formula represents the Compton scattering equation, where Δλ is the change in…
Correct answer: Δλ = h/m0c (1 - cosθ)- A. 1.02 KeV
- B. 1.02 MeV
- C. 10.2 KeV
- D. 1.00 MeV
Explanation: Pair production is a process where a photon is converted into an electron-positron pair.
Correct answer: 1.02 MeV- A. mr=nhv/2ℼ
- B. mvr=nh/2ℼ
- C. mvr=nh/2ℼr
- D. mv=nhr/2ℼ
Explanation: Bohr's postulate regarding stationary orbits states that the angular momentum (L) of an electron is quantized and can be expressed as L =…
Correct answer: mvr=nh/2ℼ- A. 24.1 nm
- B. 22.14 m
- C. 22.1 nm
- D. 22.1 mm
Explanation: The de Broglie wavelength formula is λ = h/p, where h is Planck's constant and p is the momentum of the electron.
Correct answer: 22.1 nm- A. t = t0 * √(1-v²/c²)
- B. t = t0 / √(1-v²/c²)
- C. t = t0 * (1-v²/c²)^{3/2}
- D. t = t0 / (1-v²/c²)
Explanation: The correct answer is Option B: t = t0 / √(1-v²/c²). This formula arises from the theory of special relativity and describes time…
Correct answer: t = t0 / √(1-v²/c²)- A. 0
- B. Positive
- C. Negative
- D. Positive/negative
Explanation: This is a fact. A photon is massless, has no electric charge, and is a stable particle.
Correct answer: 0- A. Property of matter and radiation
- B. Two dimensional motion
- C. Extreme velocities
- D. Small size
Explanation: In order to find the position and momentum of matter, we need to observe these metrics.
Correct answer: Property of matter and radiation- A. Microwaves, radio waves, and infra red
- B. Microwaves, radio waves, and sound
- C. Microwaves, water waves, and infra red
- D. Waves on a rope, radio waves, and infra red
Explanation: The electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical/visible light…
Correct answer: Microwaves, radio waves, and infra red- A. Dispersion
- B. Interference
- C. Reflection
- D. All of these options are correct
Explanation: White light gives a spectrum after undergoing a process called dispersion.
Correct answer: Dispersion- A. Photoelectric effect
- B. Compton effect
- C. Photoluminescence
- D. None of these options are correct
Explanation: Modern devices that use the photoelectric effect are frequently called photocells.
Correct answer: Photoelectric effect- A. Bohr
- B. Einstein
- C. Rutherford
- D. None of these option is correct
Explanation: Electronic work function, energy (or work) required to withdraw an electron completely from a metal surface.
Correct answer: Einstein- A. particle nature
- B. wave nature
- C. dual nature
- D. it transform to photon
Explanation: Electrons, when free or not under any force, roams freely, adopting their wave nature.
Correct answer: wave nature- A. Inertia
- B. Wave nature
- C. Angular momentum
- D. Linear momentum
Explanation: It is a fact that planck's constant is analogous to angular momentum as the two have the same dimensions.E=hνwhere dimensions of Energy, E…
Correct answer: Angular momentum- A. Crystals
- B. Molecules
- C. Ions
- D. Electrons
Explanation: X-rays are commonly used to investigate the structure of crystals. This is known as X-ray crystallography.
Correct answer: Crystals- A. Thermal radiation
- B. Cosmic radiation
- C. Electromagnetic radiation
- D. Non-electromagnetic radiation
Explanation: An experiment on Cosmic rays performed by Carl D Anderson led to the accidental discovery of the positron.
Correct answer: Cosmic radiation- A. 19.89 x 10^-16 J
- B. 11.89 x 10^-16 J
- C. 1.89 x 10^-16 J
- D. 19.89 x 10^-18 J
Explanation: The correct option is A.E=hf = 6.63×10-34 × 3×10¹⁸ = 19.89×10-16 J
Correct answer: 19.89 x 10^-16 J- A. 3.63 x 10^-34 Js
- B. 6.63 x 10^-34 Js-1
- C. 6.63 x 10^-34 Js
- D. 6.63 x 10^-43 Js
Explanation: Planck's Constant tells us the relationship between energy and frequency of light.The Planck constant, denoted by 'h', is a fundamental…
Correct answer: 6.63 x 10^-34 Js- A. 0
- B. λ
- C. hf/c
- D. mv
Explanation: By using the de Broglie wavelength equation.We know that λ = h/p where λ is the de broglie wavelength, h is planck's constant and p is the…
Correct answer: hf/c- A. 5.8 x 10^34
- B. 7.5 x 10^18
- C. 6.6 x 10^7
- D. 1.3 x 10^19
Explanation: Photon energy formula: E=hc/λ , where h is planck's constantλ =660nmc= 3*108 m/sh= 6.626 × 10-34 JsE=6.626*10-34 * 3*108 / 660*10-9…
Correct answer: 1.3 x 10^19