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 17 of 37
- A. Electric field
- B. Magnetic field
- C. Both A & B
- D. None of these
Explanation: X-rays do not interact significantly with electric or magnetic fields, so they cannot be deflected by either.
Correct answer: None of these- A. X-rays
- B. Beta rays
- C. Gamma rays
- D. All of these options are correct
Explanation: Pair production is a quantum phenomenon where a photon is converted into an electron-positron pair.
Correct answer: Gamma rays- A. Infrared and visible light rays
- B. All radiations
- C. Visible light and ultraviolet rays
- D. Ultraviolet and X-rays
Explanation: Black body radiations refer to the electromagnetic radiation emitted by a perfect black body, which absorbs all incident radiation and…
Correct answer: All radiations- A. -0.0136 eV
- B. -1.136 eV
- C. 0.136 eV
- D. None of these options is correct
Explanation: The correct formula to calculate the energy of an electron in the nth orbit of a hydrogen atom is given by the Rydberg formula:En=−13.6…
Correct answer: None of these options is correct- A. Annihilation of matter
- B. Anti-pair production
- C. Materialization of matter
- D. Annihilation of practical into its anti-particle
Explanation: When a particle and its antiparticle collide, they annihilate each other, converting their mass into energy according to Einstein's famous…
Correct answer: Annihilation of matter- A. Infrared
- B. Violet
- C. Blue
- D. Ultraviolet
Explanation: Photon energy is inversely proportional to the wavelength of light. This means that shorter wavelengths correspond to higher energy…
Correct answer: Ultraviolet- A. λ
- B. 3λ
- C. 4λ
- D. λ/2
Explanation: In wave motion, the least distance between two points that are out of phase by π radians (180 degrees) is referred to as half of the…
Correct answer: λ/2- A. 4.770 x 10^21
- B. 3.770 x 10^11
- C. 3. 770 x 10^21
- D. 3.770 x 10^22
Explanation: The explanation is given below:l= 1500 W/m^2λ=5000ÅE= hfE= hc/λAs c is the speed of light = 3×10^8 h is plank's constant =6.626 × 10^-34…
Correct answer: 3. 770 x 10^21- A. Intensity of incident light
- B. Energy of incident light
- C. Wavelength of incident light
- D. Frequency of incident light
Explanation: The intensity of incident light refers to the brightness or the amount of light energy falling on the metal surface per unit area per unit…
Correct answer: Intensity of incident light- A. 12.6 x 10^6 Hz
- B. 19.6 x 10^6 Hz
- C. 1.6 x 10^16 Hz
- D. 81.6 x 10^6 Hz
Explanation: The explanation is given below:Frequency can be written as f = E/h f = (66.3x1.6 x 10^-19) / (6.63x10^-34) f = 1.6 x 10^16 Hz
Correct answer: 1.6 x 10^16 Hz331. What will be the De-Broglie wavelength when the kinetic energy of the electron increases by 5 times?
- A. √5
- B. 5
- C. 1/√5
- D. 1/5
Explanation: The de Broglie wavelength (λ) of a particle is given by the λ = where h is the Planck's constant (approximately 6.626 x 10^-34…
Correct answer: 1/√5- A. 8.8 x 10^-34 m
- B. 8.8 x 10^-35 m
- C. 8.8 x 10^-20 m
- D. 8.8 x 10^-25 m
Explanation: The explanation is given below:λ = h/рp = m x v ; 150/1000 x 50 = 7.5 6.63 x 10-34/7.5 = 8.8 x 10-35
Correct answer: 8.8 x 10^-35 m- A. Remains same
- B. Increases
- C. Decreases
- D. None of these
Explanation: In Compton's scattering process, the wavelength of scattered X-ray increases.
Correct answer: Increases- A. Line
- B. Continuous
- C. Band
- D. All of these options are correct
Explanation: The spectrum of a black body is continuous, meaning it contains a continuous range of wavelengths without any distinct breaks or lines.
Correct answer: Continuous- A. 700Å - 1000Å
- B. 1nm - 100nm
- C. 0.1nm - 1nm
- D. 4000Å - 7000Å
Explanation: The range of wavelengths of visible light is approximately 4000 angstroms (Å) to 7000 angstroms (Å).
Correct answer: 4000Å - 7000Å- A. Emitted
- B. Absorbed
- C. Travelling
- D. All of these options are correct
Explanation: Since the uncertainty in position and momentum applies to X-ray photons regardless of whether they are emitted, absorbed, or traveling.
Correct answer: All of these options are correct- A. Less
- B. High
- C. Equal
- D. None of these options are correct
Explanation: White light consists of photons with a range of energies corresponding to different wavelengths in the visible spectrum.
Correct answer: Less- A. Translucent glass box
- B. Cavity Radiator
- C. Black holes
- D. All of these options are correct
Explanation: A perfect black body at a constant temperature absorbs and re-emits all the electromagnetic radiation that falls on it.
Correct answer: Cavity Radiator- A. Inversely proportional
- B. Directly proportional
- C. Equal
- D. None of these
Explanation: Einstein's equation E=mc^2 implies a direct proportionality between mass and energy.
Correct answer: Directly proportional- A. Phosphorous
- B. Carbon
- C. Sodium
- D. X-ray phosphors
Explanation: X-ray phosphors are indeed the materials commonly used in X-ray detection screens, as they absorb X-rays and emit visible light, enabling…
Correct answer: X-ray phosphors