Free Photons and the Particle Model of Light MCQs with Answers
12 Photons and the Particle Model of Light MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
12 questions · page 2 of 2
11. The momentum of a photon of wavelength lambda is
- A. h divided by lambda
- B. h times lambda
- C. zero, since a photon has no mass
- D. mc
Explanation: A photon has zero rest mass but still carries momentum h over lambda, which is what allows radiation pressure and the recoil seen in the Compton effect. Solar sails are propelled by exactly this momentum transfer. Assuming that no rest mass means no momentum is the standard misconception here.
Correct answer: h divided by lambda12. The photoelectric effect is best demonstrated with which metal, given that it has a very low work function?
- A. Caesium
- B. Iron
- C. Tungsten
- D. Platinum
Explanation: Caesium's work function is only about 2 eV, so ordinary visible light is enough to eject electrons, whereas tungsten and platinum need ultraviolet. This is why alkali metals are used in photocells and photomultipliers. The low value reflects how loosely the single outer electron of an alkali metal is held.
Correct answer: Caesium