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 21 of 37
- A. length-contraction
- B. space-time interval
- C. space-time geometry
- D. mass-energy equivalence
Explanation: Einstein's theory of relativity transformed the understanding of gravity from a force acting at a distance, as in Newtonian physics, to an…
Correct answer: space-time geometry- A. the velocity of light
- B. half the velocity of light
- C. twice the velocity of light
- D. thrice the velocity of light
Explanation: The special theory of relativity postulates that as an object with mass accelerates towards the speed of light, its relativistic mass…
Correct answer: the velocity of light- A. less than the incident photon
- B. less than the scattered electron
- C. larger than the incident photon
- D. larger than the scattered electron
Explanation: Compton's effect describes the scattering of X-rays by free electrons, where the incident X-ray photon transfers part of its energy and…
Correct answer: larger than the incident photon- A. 10 m/sec
- B. 1 x 10^3 m/ sec
- C. 1 x 10^4 m/ sec
- D. 1 x 10^6 m/ sec
Explanation: Convert the wavelength to meters: 3000 Å = 3000 x 10-10 m = 3 x 10-7 m Calculate the energy of the incident photon (E) using the formula E…
Correct answer: 1 x 10^6 m/ sec- A. 2 times of the earlier value
- B. More than 2 times of the earlier value
- C. Less than 2 times of the earlier value
- D. Unchanged
Explanation: Le hv0−W0=KIf frequency is doubled, let kinetic energy of photoelectrons be K12hv−W0=K1⇒2(hv−W0)+W0=K1⇒2K+W0=K1Kinetic energy will be more…
Correct answer: More than 2 times of the earlier value- A. hλ
- B. h/λ
- C. λ/h
- D. h2/λ2
Explanation: E = pc hc/λ = pc p = h/λ Hence, option B is correct.
Correct answer: h/λ- A. E2-E1/hc
- B. hc/E2-he/E1
- C. hc/E2-E1
- D. c/h(E2-E1)
Explanation: By quantum theory of radiation, the energy change E between energy levels is proportional to the frequency of electromagnetic radiation f…
Correct answer: hc/E2-E1- A. Compton effect
- B. Photoelectric effect
- C. Pair production
- D. Black body radiation
Explanation: The photoelectric effect refers to the phenomenon where photons are absorbed by a photo-sensitive surface, resulting in the ejection of…
Correct answer: Photoelectric effect- A. Greater energy
- B. Greater frequency
- C. Greater energy and momentum
- D. Equal energy
Explanation: The correct statement is C. Greater energy and momentum. In the Compton effect, the incident photon has greater energy and momentum…
Correct answer: Greater energy and momentum- A. Longer
- B. Shorter
- C. Same
- D. Infinite
Explanation: In Compton effect, the wavelength of the scattered photon is higher than that of the incident photon.
Correct answer: Longer- A. Frequency
- B. Kinetic energy
- C. Intensity
- D. Momentum
Explanation: In the photoelectric effect, when the frequency of light exceeds a certain threshold frequency, photons can eject electrons from a…
Correct answer: Intensity- A. Reverse bias
- B. Forward bias
- C. No bias
- D. Zener bias
Explanation: This is the correct answer. Photodiodes are typically operated in reverse bias mode.
Correct answer: Reverse bias- A. The law of conservation of mass only
- B. Law of conservation of mass-energy
- C. law of conservation of energy only
- D. All of the above
Explanation: In the special theory of relativity, Albert Einstein showed that mass (m) and energy (E) are equivalent and can be converted into each…
Correct answer: Law of conservation of mass-energy- A. The scattering of the light by prism
- B. The bending of light when it passes from one medium to another
- C. The change in the wavelength of X-rays when they interact with matter
- D. The creation of interference patterns in a double-slit experiment
Explanation: The Compton effect is a phenomenon in physics where the wavelength of X-rays or gamma rays changes when they interact with matter…
Correct answer: The change in the wavelength of X-rays when they interact with matter- A. A photon of wavelength 1nm
- B. A photon of wavelength 50 μm
- C. A photon of wavelength 2 pm
- D. A photon of wavelength 200 nm
Explanation: A photon of wavelength 2 pmExplanation:The energy (E) of a photon is related to its wavelength (λ) by the equation: E = hc / λ, where h is…
Correct answer: A photon of wavelength 2 pm- A. Waves, particles
- B. Particles, waves
- C. Particles, particles
- D. Waves, waves:
Explanation: Explanation: Wave-particle duality states that micro-particles exhibit both wave-like and particle-like properties.
Correct answer: Waves, particles- A. 1905
- B. 1927
- C. 1929
- D. 1937
Explanation: Explanation: Louis de Broglie received the Nobel Prize in Physics in 1929 for his discovery of the wave nature of electrons.
Correct answer: 1929- A. One
- B. Infinite
- C. Zero
- D. Depends on frequency
Explanation: Explanation:Photons are massless particles. They have energy and momentum due to their motion, but their rest mass is zero.
Correct answer: Zero- A. 7.9×10^−48 J
- B. 7.9×10^−40 J
- C. 7.9×10^−28 J
- D. 7.9×10^−19 J
Explanation: Explanation:E = hf, where h is Planck's constant (6.63 × 10^-34 J·s) and f is frequency.
Correct answer: 7.9×10^−19 J- A. 1.023V
- B. 1.026V
- C. 1.02MeV
- D. 1.02GeV
- E. 1.02keV
Explanation: The rest-mass energy of each of these charged particles is equivalent to 0.511 MeV and, therefore, pair production is not possible below a…
Correct answer: 1.02MeV