Question
As a large object (such as a 3,000 kg car) accelerates, what is the trend in its de Broglie wavelength?
(A) Its de Broglie wavelength gets smaller.
(B) Its de Broglie wavelength gets bigger.
(C) Its de Broglie wavelength remains the same.
(D) Any object with rest mass would have to go faster than the speed of light to have a measurable de Broglie wavelength.
▶️Answer/Explanation
Ans:(A)
Since λ = h / mv , as v gets bigger, wavelength decreases.
Question
Which of the following photons has the largest momentum?
(A) X ray
(B) Ultraviolet
(C) Infrared
(D) None of these has momentum
▶️Answer/Explanation
Ans:(A)
According to Compton, the momentum of a photon is p = hf / c . The photon with the highest frequency has the highest momentum.
Question
Which of the following photons has the largest momentum?
(A) X ray
(B) Ultraviolet
(C) Infrared
(D) None of these has momentum
▶️Answer/Explanation
Ans:(A)
According to Compton, the momentum of a photon is p = hf / c . The photon with the highest frequency has the highest momentum.
Question
Which of the following phenomena can be better understood by considering the wave- particle duality of electrons? (Select two answers.)
(A) There are discrete electron energy levels in a hydrogen atom.
(B) Monochromatic light of various intensities eject electrons of the same maximum energy from a metal surface.
( C) A beam of electrons reflected off the surface of a crystal creates a pattern of alternating intensities.
(D) An X-ray colliding with a stationary electron causes it to move off with a velocity.
▶️Answer/Explanation
Ans:A and C
The discrete electron energy levels in hydrogen can be understood as being orbits of constructive wave interference locations for the electron. The alternating intensities seen in diffraction patterns are evidence of the wave nature of electrons reflecting off the atoms in the crystal. Both of the other choices are examples of the particle nature of electromagnetic waves.
Question
Which of the following best supports the particle nature of light?
(A) Compton Effect
(B) Diffraction
(C) Doppler Effect
(D) Interference
▶️Answer/Explanation
Ans: (A)
The Compton Effect showed that photons have momentum and they obey the laws of conservation of energy and conservation of momentum.
Question
An alien space ship attacks a planet by shooting a laser beam at the planet every five seconds. If the ship is approaching the planet at high speed, which of the following is true for an observer situated on the planet?
(A) The laser beams strike the planet at a frequency of 0.2 Hz.
(B) The laser beams strike the planet at a frequency less than 0.2 Hz.
(C) The laser beams strike the planet at a frequency greater than 0.2 Hz.
(D) More information is needed.
▶️Answer/Explanation
Ans: (C)
The laser beams strike the planet at a frequency greater than 0.2 Hz. As the spaceship approaches the planet while emitting laser beams at a frequency of 0.2 Hz, the observer on the planet will observe a frequency shift to a higher frequency consistent with the Doppler Effect.