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 14 of 37
261. All motions are:
- A. Absolute
- B. Relative
- C. Uniform
- D. None of these
Explanation: "All motions are relative."This statement reflects the principle of relativity in physics, which is a fundamental concept introduced by…
Correct answer: Relative- A. The most efficient radiator
- B. A perfect absorber of radiation
- C. A body whose absorber power is unity
- D. All of the above
Explanation: A black body absorbs all incident radiation without reflecting or transmitting any of it.
Correct answer: All of the above- A. A white towel
- B. Black wool blanket
- C. A polished plate
- D. None of the above
Explanation: A good absorber of heat radiation is typically a material that appears dark and has a high emissivity.
Correct answer: Black wool blanket- A. Stopping potential
- B. Electromotive force
- C. Work function
- D. Threshold frequency
Explanation: The work function is the minimum energy needed to remove an electron from a solid to a point in the vacuum immediately outside the solid…
Correct answer: Work function- A. Decreases by an amount equal to half of an incident photon of wavelength λ
- B. Increases by an amount equal to four times energy of an incident photon of wavelength λ
- C. Increases by an amount equal to the work function of the metal
- D. Decreases by an amount equal to the energy of an incident photon of wavelength λ
Explanation: The maximum kinetic energy KEe of ejected electrons (photoelectrons) is given by KEe=hf−BE , where hf is the photon energy and BE is the…
Correct answer: Increases by an amount equal to four times energy of an incident photon of wavelength λ- A. Stopping potential increases
- B. Stopping potential decreases
- C. Stopping potential remains constant
- D. Stopping potential becomes infinite
Explanation: The stopping potential is the voltage required to completely stop photoelectrons.
Correct answer: Stopping potential increases- A. 1.99 x 10^-15 J
- B. 3 x 10^8 J
- C. 6.6 x 10^-34 J
- D. 19.89 x 10^-26 J
- E. 1.99 J
Explanation: ->v=fλ3 x 108=f x (1.0 X 10-10)f=3 x 108/1.0 X 10-10=3 x 1018->E=hfE=(6.62607004 × 10-34 )*(3 x 1018)=1.99 x 10-15
Correct answer: 1.99 x 10^-15 J- A. I only
- B. II only
- C. III only
- D. I and III only
- E. I, II and III
Explanation: Gamma ray photons can interact with matter in all of the ways described above.
Correct answer: I, II and III- A. 1/300000
- B. 1/600000
- C. 1/900000
- D. 1/1200000
- E. 1/1500000
Explanation: The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600000 square meters of a blackbody at the…
Correct answer: 1/600000- A. Photoelectric Effect
- B. Compton's Effect
- C. Henry's Effect
- D. Principle of Relativity
- E. Coulomb's Law
Explanation: When a metal surface is exposed to a monochromatic electromagnetic wave of sufficiently short wavelength (or equivalently, above a…
Correct answer: Photoelectric Effect- A. Annihilation
- B. Pair production
- C. Compton scattering
- D. Photoelectric effect
Explanation: This is the correct answer. When an electron and its antiparticle, a positron, come into contact, they undergo a process called…
Correct answer: Annihilation- A. 3.61 x 10^-19 J
- B. 4.55 x 10^-29 J
- C. 5.13 x 10^-19 J
- D. 6.13 x 10^-19 J
- E. 8.71 x 10^-19 J
Explanation: KE = 1/2mv2KE = ½(9.11 x 10-31)(10)2KE = 4.55 x 10-29 J
Correct answer: 4.55 x 10^-29 J273. Minimum frequency below which no electrons are emitted from the metal surface is called _ frequency.
- A. Minimum
- B. Angular
- C. Maximum
- D. Threshold
Explanation: The correct answer is the 'threshold frequency', which is the minimum frequency of electromagnetic radiation necessary to dislodge…
Correct answer: Threshold- A. Huygen
- B. Fraunhofer
- C. Fresnel
- D. Coulomb
- E. Maxwell
Explanation: James Clerk Maxwell is credited with formulating the electromagnetic wave theory in 1864.
Correct answer: Maxwell- A. 0.6 x 10^-15 J
- B. 1.98 x 10^-15 J
- C. 3.7 x 10^-15 J
- D. 4.7 x 10^-15 J
- E. 7.7 x 10^-15 J
Explanation: So, the energy of x rays is 1.98 x 10 -15 J. Hence, this is the required solution.
Correct answer: 1.98 x 10^-15 J- A. Photoelectric effect
- B. Pair production
- C. X-ray production
- D. Gamma ray production
- E. Radioactive capture
Explanation: Photoelectric effect, a phenomenon in which electrically charged particles are released from or within a material when it absorbs…
Correct answer: Photoelectric effect- A. The objective observations
- B. Measurement of natural phenomena
- C. Study of chemical solutions only
- D. Both A and B
Explanation: Physics depends on objective observations and measurement of natural phenomena.Not on studying chemical solutions,which is actually…
Correct answer: Both A and B- A. Rectilinear path
- B. Circular path
- C. Geodesics
- D. Parabolic
Explanation: Geodesics: This is the correct option. According to Einstein's general theory of relativity, bodies and light rays follow paths called…
Correct answer: Geodesics- A. Intermediate wavelengths
- B. Longer wavelengths
- C. Shorter wavelengths
- D. Low frequencies
Explanation: According to Wien's Law, as the temperature of the blackbody increases, the wavelength of emitted radiations decreases.Hence the answer is…
Correct answer: Shorter wavelengths- A. 8
- B. 10
- C. 7
- D. None
Explanation: 7-segment Displays can be used together to display digits from 0 to 9 as well as a few...
Correct answer: 7