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 24 of 37
- A. Photoelectric effect
- B. Interference
- C. Polarization
- D. Matter waves
Explanation: The phenomenon in which an incident ray of light is ejected from the surface of a metal when light is incident on it, is called the…
Correct answer: Photoelectric effect- A. Momentum
- B. Frequency
- C. Mass
- D. All of these
Explanation: Wave-particle duality does not directly explain mass. Mass is a property of particles that is described within the framework of classical…
Correct answer: Mass- A. Particle nature
- B. Wave nature
- C. Dual nature
- D. It transforms into a photon
Explanation: According to the principles of quantum mechanics, electrons (and other particles) exhibit both wave-like and particle-like behavior.
Correct answer: Dual nature- A. Alpha
- B. Gamma
- C. Beta
- D. White
Explanation: Gamma radiation consists of high-energy photons emitted from the nucleus of an atom during radioactive decay or other nuclear processes.
Correct answer: Gamma- A. Photon
- B. X
- C. Beta
- D. White
Explanation: X-rays are a form of electromagnetic radiation used in medical scanning, such as X-ray imaging, CT scans, and fluoroscopy.
Correct answer: X- A. Interference
- B. Reflection
- C. Polarization
- D. Photoelectric effect
Explanation: The photoelectric effect is a phenomenon that can only be explained by considering the particle nature of light.
Correct answer: Photoelectric effect- A. Burning
- B. Cancer
- C. Flu
- D. All of these
Explanation: Radiation exposure can indeed cause burning (radiation burns), and cancer (by damaging DNA and causing mutations), and although radiation…
Correct answer: All of these- A. Emits all radiation
- B. Absorbs all radiation
- C. Both Options A and B are correct
- D. None of these options are correct
Explanation: An ideal black body is a perfect absorber as well as perfect emitter of electromagnetic radiation. Hence, Option C is correct.
Correct answer: Both Options A and B are correct- A. Intermediate wavelengths
- B. Long wavelengths
- C. Short wavelengths
- D. Low frequencies
Explanation: Wein's displacement law states that temperature is inversely related to wavelength.
Correct answer: Short wavelengths- A. Alpha
- B. Gamma
- C. Beta
- D. All
Explanation: A black body is an idealized object that absorbs all electromagnetic radiation so technically they all pass.
Correct answer: All- A. Diffractions
- B. Interference
- C. Photoelectric effect
- D. Polarization
Explanation: The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material.
Correct answer: Photoelectric effect- A. I only
- B. II only
- C. I and II
- D. None of the above
Explanation: 1. I is the first postulate of newton's theory of relativity which states that laws of physics are only same in inertial frames so I is…
Correct answer: I and II- A. Fe
- B. MgO
- C. I
- D. ZnS
Explanation: When cathode rays strike ZnS (zinc sulfide), it emits a green glow. When zinc sulfide gets hit by electrons of the cathode rays, electrons…
Correct answer: ZnS- A. 15 Joule
- B. 10 x 10^-19 Joule
- C. 4 x 10^-19 Joule
- D. None of these
Explanation: Φ = hc/λ (where Φ is the work function, h is the Planck constant, c is the speed of light and λ is the wavelength) Φ = (6.63x10-34 x…
Correct answer: 4 x 10^-19 Joule- A. hf/c
- B. hf/c2
- C. c2/hf
- D. hfc
Explanation: Using the equations E = hf Where E is the energy, h is Planck's constant, and f is the frequency Also the equation E = mc2 Where E is the…
Correct answer: hf/c2- A. each carries one-quarter of their previous momentum
- B. each carries one-quarter of their previous energy
- C. are one-quarter as numerous
- D. are half as numerous
Explanation: The intensity of light is inversely proportional to the square of the distance between the light source and the photocell.
Correct answer: are one-quarter as numerous- A. 0.9 eV
- B. 1.7 eV
- C. 2.2 eV
- D. 3.1 eV
Explanation: Let's first calculate the energy of the first radiation. Energy = hv/λ = (6.63x10-34 x 3x108)/ 400x10-9 = 4.9725x10-19 J = 4.9725x10-19 /…
Correct answer: 2.2 eV- A. 309 nm
- B. 209 nm
- C. 109 nm
- D. 9 nm
Explanation: This is the following solution: Based on the calculations, the approximate longest wavelength of light that can cause photoemission is (A)…
Correct answer: 309 nm- A. 6.2 x 10^20
- B. 3 x 10^19
- C. 1.5 x 10^20
- D. 6 x 10^18
Explanation: EEnergy of photon = (6.6 x 10 ^-34)(3 x 10^8)/0.6 x 10 ^-6E = 33 x 10 ^-20 JNumber of photons emitted per second is given by:N = 25/100…
Correct answer: 1.5 x 10^20- A. Huygen wave theory
- B. Photoelectric effect
- C. Maxwell electromagnetic theory
- D. de-Broglie theory
Explanation: The photoelectric effect is the process in which electromagnetic radiation ejects electrons from a material.
Correct answer: Photoelectric effect