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 28 of 37
- A. A surface coated with lamp black
- B. A hollow cavity within a solid body
- C. A highly polished black body
- D. A tungsten filament
Explanation: A black body, in theory, is an idealized object that absorbs all incident electromagnetic radiation.
Correct answer: A hollow cavity within a solid body- A. Zero
- B. Infinite
- C. One
- D. 1/2
Explanation: The absorptive power of a body or a surface is defined as the ratio of the energy absorbed in a given time to the radiant energy incident…
Correct answer: One- A. Reflectors
- B. Absorbers
- C. Radiators
- D. Emitters
Explanation: White clothes are worn on hot days or in hot climates because they are good at reflecting sunlight.
Correct answer: Reflectors- A. Special theory of relativity
- B. Quantum theory
- C. Corpuscular theory
- D. Bohr's theory
Explanation: The theory that explains that energy exchange takes place in discrete "bundles" or "quanta" is quantum theory.
Correct answer: Quantum theory- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: E = hf This equation is a key element in understanding the quantization of energy in quantum theory.
Correct answer: Option B- A. Proton
- B. Electron
- C. Neutron
- D. Photon
Explanation: The light particle conceived by Einstein is called a photon. Photons exhibit both wave-like and particle-like properties, and they play a…
Correct answer: Photon- A. Einstein
- B. Ampere
- C. Thomson
- D. Planck
Explanation: Einstein introduced the concept of the photon in a 1905 paper on the photoelectric effect, where he proposed that light is quantized into…
Correct answer: Einstein- A. 1.6 x 10^-19 Joule-second
- B. 6.63 x 10^-34 Joule-second
- C. 6.63 x 10^-54 Joule-second
- D. None of the above
Explanation: The magnitude of Planck's constant h is approximately 6.626×10−34 joule-sec.
Correct answer: 6.63 x 10^-34 Joule-second- A. 3 x 10^8 ms-1
- B. 3 x 10^8 cms-1
- C. 3 x 10^2 ms-1
- D. 6 x 10^8 ms-1
Explanation: The velocity of a photon in a vacuum is constant and is equal to the speed of light c, which is approximately 3 x 10-8 m/s.
Correct answer: 3 x 10^8 ms-1- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: The energy of photon is given by: E = hf This equation expresses the quantization of energy in quantum mechanics and demonstrates that the…
Correct answer: Option B- A. Photoelectric effect
- B. Compton effect
- C. Photo cell
- D. The uncertainty principle
Explanation: The phenomenon of electron ejection by light is called the "photoelectric effect." In the photoelectric effect, electrons are emitted from…
Correct answer: Photoelectric effect- A. 1905
- B. 1921
- C. 1925
- D. 1934
Explanation: Albert Einstein was awarded the Nobel Prize in Physics in 1921 for his explanation of the photoelectric effect.
Correct answer: 1921- A. Einstein
- B. Planck
- C. Hertz
- D. Lenar
Explanation: The photoelectric effect was explained by Albert Einstein. In 1905, Einstein published a seminal paper in which he proposed that light…
Correct answer: Einstein- A. Protons
- B. Positrons
- C. Electrons
- D. Neutrons
Explanation: The photoelectric effect occurs when an x-ray interacts with an electron in the matter.
Correct answer: Electrons- A. Wave nature
- B. Particle nature
- C. Both particle and wave nature
- D. All of the above
Explanation: In the photoelectric effect, light exhibits both wave-like and particle-like properties.
Correct answer: Both particle and wave nature- A. Compton effect
- B. Photoelectric effect
- C. Photo refraction
- D. Gama-rays counter
Explanation: A photoelectric cell operates based on the photoelectric effect. The key principle involved is the emission of electrons from a material…
Correct answer: Photoelectric effect- A. Compton effect
- B. Threshold frequency
- C. Work function
- D. Pair production
Explanation: The amount of energy required to eject an electron from the surface of a metal is known as the "work function" (W).
Correct answer: Work function- A. Heat
- B. Energy
- C. Power
- D. Planck's constant
Explanation: The joule-second (J·s) is the unit of action or angular momentum. It is often used to express the value of the reduced Planck constant.
Correct answer: Planck's constant- A. Interference
- B. Photoelectric effect
- C. Diffraction
- D. None of the above
Explanation: The phenomenon in which electromagnetic radiations, such as light, exhibit particle-like properties is the "photoelectric effect." In the…
Correct answer: Photoelectric effect- A. Photoelectric emission
- B. Thermionic emission
- C. Oscillatory current
- D. None of the above
Explanation: The phenomenon in which electric charges (electrons) are emitted from hot bodies is known as "thermionic emission." In thermionic…
Correct answer: Thermionic emission