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 19 of 37
- A. Constant velocity
- B. Zero velocity
- C. Zero acceleration
- D. All of these
Explanation: An inertial frame can indeed have objects with constant velocity, zero velocity, and zero acceleration.
Correct answer: All of these- A. Infinite rest mass
- B. Rest mass but no charge
- C. No rest mass and no charge
- D. A and C are correct
Explanation: Photons are massless particles with no rest mass. They also do not carry any electric charge.
Correct answer: No rest mass and no charge- A. Charge
- B. Momentum
- C. Both A & B
- D. None of these
Explanation: In pair production, a photon is absorbed by matter, typically an atomic nucleus, and converts its energy into the mass of an…
Correct answer: Both A & B- A. 1 nm
- B. 0.5 nm
- C. 0.0056 nm
- D. 0.086 nm
Explanation: λ = h/pWe can find the momentum of the electron from the potential difference:qV = 1/2 mv^2 = p^2/(2m)Solving for p, we get:p =…
Correct answer: 0.086 nm- A. X-rays
- B. Beta rays
- C. Gamma rays
- D. All of these options are correct
Explanation: Beta rays consist of high-energy electrons or positrons emitted from the nucleus of a radioactive atom during beta decay.
Correct answer: Beta rays- A. Burning
- B. Cancer
- C. Flu
- D. Both A and B
Explanation: Radiation is energy that comes from a source and travels through space at the speed of light.
Correct answer: Both A and B- A. Long
- B. Short
- C. Absorbed immediately
- D. Never-ending distance
Explanation: Gamma rays travel long distances. Gamma rays are a form of electromagnetic radiation, like light and X-rays, but with much higher energy…
Correct answer: Long- A. Emits
- B. Absorbs
- C. Both Options A and B are correct
- D. Reflects
Explanation: A black body absorbs all radiation incident upon it, regardless of wavelength or frequency.
Correct answer: Both Options A and B are correct- A. Telescope
- B. Turntable
- C. Cross wire of telescope
- D. None of these options are correct
Explanation: In a spectrometer, the circular scale graduated in half degrees is typically attached to the turntable.
Correct answer: Turntable- A. Wave nature
- B. Particle nature
- C. Dual nature
- D. It never moves when in bound state
Explanation: The bound state electron has a dual nature.Dual nature refers to the concept in quantum mechanics that particles, such as electrons, can…
Correct answer: Dual nature- A. 7.3 x 10^-34 J Hz-1
- B. 9.3 x 10^-34 J Hz-1
- C. 8.3 x 10^-34 J Hz-1
- D. 6.63 x 10^-34 J Hz-1
Explanation: Planck's constant is a fundamental constant, equal to the energy of a quantum of electromagnetic radiation divided by its frequency, with…
Correct answer: 6.63 x 10^-34 J Hz-1- A. Absorbed
- B. Both of these
- C. Emitted
- D. None of these
Explanation: A black body absorbs electromagnetic radiations and then emits electromagnetic thermal radiations (also known as black body radiations)…
Correct answer: Both of these- A. De-excitation
- B. Photoelectric effect
- C. Excitation
- D. Ionization
Explanation: De-excitation is the transition of electrons from higher to lower energy states, with the release of energy as photons.
Correct answer: De-excitation- A. Long wavelength rays
- B. Low energy waves
- C. Low frequency rays
- D. Short wavelength rays
Explanation: X-rays are highly energetic, high frequency and short wavelength radiations. Their wavelength is in the range 0.01-10 nm.
Correct answer: Short wavelength rays- A. Newton
- B. Heisenberg
- C. Einstein
- D. Bohr
Explanation: Work function is the minimum energy required to cause the photoelectric effect. It is constant for a particular material.
Correct answer: Einstein- A. Not greater than hc/eV
- B. . Not less than hc/eV
- C. Equal to the h/mV
- D. Greater than or equal to hc/eV
Explanation: Greater than or equal to hc/eV: This option suggests that the wavelength of emitted X-rays is at least equal to the value of hc/eV.
Correct answer: Greater than or equal to hc/eV- A. K.E. = e2V
- B. K.E. = hc/λ
- C. K.E. = hf2
- D. K.E. = eV
Explanation: An electron cannot travel at the speed of light, unless the wave properties are being studied it's wavelength cannot be observed; however…
Correct answer: K.E. = eV- A. [LT-1]
- B. [ML2T-2]
- C. [MLT-1]
- D. [MLT-2]
Explanation: The equation x = mc² represents the relationship between mass and energy, where x is the energy equivalent of a mass m, and c is the speed…
Correct answer: [ML2T-2]- A. Electrons being emitted by the solids through photoelectric effect when irradiated with electromagnetic radiation
- B. Incident electrons colliding with electrons in solids and releasing doubling the number of incident electrons
- C. Electrons in solids are emitted without any external stimulus through radiation
- D. Excited electrons going back to lower energy states immediately by releasing energy.
Explanation: Spontaneous emission is the process in which a molecule, an atom or a subatomic particle transits from an excited energy state to a lower…
Correct answer: Excited electrons going back to lower energy states immediately by releasing energy.- A. K.E. = eV
- B. K.E. = hλmin/c
- C. K.E. = hc/λmin
- D. K.E. = h/λmax
Explanation: According to the photoelectric equation:(KE)max = Energy of incident photon - Work functionOnly A is correct because eV is one way of…
Correct answer: K.E. = eV