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 25 of 37
- A. I/2
- B. 2I
- C. I
- D. 4I
Explanation: Lenses of the same diameter collect equal amount of light. Intensity is the measure of amount of light colleted, hence the intnensity…
Correct answer: I- A. diffraction and photoelectric effect
- B. diffraction and reflection
- C. diffraction and interference
- D. photoelectric effect
Explanation: Diffraction exhibits wave nature of light and photoelectric effect exhibits quantum nature of light.
Correct answer: diffraction and photoelectric effect- A. 1 : 2
- B. 2 : 1
- C. 4 : 1
- D. 1 : 4
Explanation: Since this question skips the part about the kinetic energy of the emitted electrons, we are to assume that the energy delivered by the…
Correct answer: 2 : 1- A. 4λ
- B. 2λ
- C. λ/2
- D. λ/4
Explanation: HgWo = h c/λ (i) 2Wo= h c/λ1 (ii) Putting equation (i) equal to (ii), we get2=λ/λ1 or λ1=λ/2 1 (ii)
Correct answer: λ/2- A. 1017
- B. 1019
- C. 1021
- D. 1015
Explanation: P=100 x 3 / 100= 3 Watts λ=6625 A= 6625x 10^-10 m P=Nhc/λt N=Pλt/hc 3 x 6625 x 10^-16 x 1 / 6.625x10^-34 x 3 x 10^9 N=10^19
Correct answer: 1019- A. 1/√8
- B. √2
- C. 1/√2
- D. 2
Explanation: The de Broglie wavelength (λ) of a particle is given by the equation λ = h / p, where h is Planck's constant and p is the momentum of the…
Correct answer: 1/√2- A. Total energy
- B. Total momentum
- C. Number of photons
- D. None of these
Explanation: In a photon - particle collision, the number of photons may not be conserved. The photon may be absorbed or a new photon may be created.
Correct answer: Number of photons- A. 0.61 x 10^-26 erg
- B. 2.0 x 10^-26 erg
- C. 6 x 10^-6 erg
- D. 6 x 10^-8 erg
Explanation: P = E /c E = p*c = (2x10-16) x (3x108) = 6x10-8 erg
Correct answer: 6 x 10^-8 erg- A. 1.6 x 10^28
- B. 1.6 x 10^29
- C. 1.6 x 10 30
- D. 1.6 x 10 32
Explanation: This is the correct option.E = hf = 6x10^-26Power = 10kWTotal photons in one sec N = P/E = (10 x10^3)/(6x10^-26 ) = 1.6 x 10^29
Correct answer: 1.6 x 10^29- A. 10-27 Kg ms-1
- B. 9 x 10^-11 Kg ms-1
- C. 10-11 Kg ms-1
- D. 3 x 10^-11 Kg ms-1
Explanation: E = Pc P = E/c P = 3x10^-19/3x10^8 P=10^-27 kgms -1
Correct answer: 10-27 Kg ms-1- A. 1 amu
- B. 9 x 10^-31 kg
- C. 1.67 x 10^-35 kg
- D. Zero
Explanation: The rest mass of photon is zero. The mass of any particle at rest (relative to the observer) is known as the rest mass of that particle.
Correct answer: Zero- A. pc/h
- B. hc/p
- C. ph/c
- D. h/pc
Explanation: The momentum of a photon is given by p = E/c, where E is the energy of the photon and c is the speed of light.
Correct answer: pc/h- A. 2:1
- B. 1:2
- C. 1:1
- D. None of these
Explanation: E=Pc P is directly proportional to E PA/PB = EA/EB = 2EB/EB = 2/1
Correct answer: 2:1- A. 6.63 x 10^-34 Js-1
- B. 6.63 x 10^-34 Js
- C. 6.63 x 10^-42 Js
- D. 3.63 x 10^-34 Js
Explanation: Option B is correct.The value of Planck's constant 'h' can be expressed in different units.
Correct answer: 6.63 x 10^-34 Js- A. nr = nb
- B. nr < nb
- C. nr> nb
- D. The information is insufficient to get a relation between nr and nb
Explanation: Option C is correct.The number of photons emitted by the red bulb is greater than the number of photons emitted by the blue bulb.
Correct answer: nr> nb- A. 1/E for both photons and particles
- B. 1/√ E for both photons and particles
- C. 1/E for photons and 1/√ E for particles
- D. 1/√ E for photons and 1/E for particles
Explanation: Option C is correct.The wavelength of a photon is inversely proportional to its energy, but for particles, the wavelength is inversely…
Correct answer: 1/E for photons and 1/√ E for particles- A. A.
- B. B.
- C. C.
- D. D.
Explanation: Option D is correct.The inversely proportional graph correctly represents the variation of particle momentum with associated de Broglie…
Correct answer: D.- A. h/moc
- B. moc/h
- C. 0
- D. ∞
Explanation: λ = h/moc is expression for De-Broglie wavelength. The explanation is given below:
Correct answer: 0- A. Energy
- B. Wavelength and frequency
- C. Momentum
- D. All of these
Explanation: Option Dis correct.1.A photon is considered to have energy. The energy of a photon is given by the following equation: E = hν where: h is…
Correct answer: All of these- A. Electron
- B. Proton
- C. Both have same
- D. Electron and Proton cannot have wavelength
Explanation: Option A is correct.The electron is much lighter than the proton (approximately 1836 times lighter), for them to have the same momentum…
Correct answer: Electron