If the wavelength of incident radiation is increased in photoemission then_________________?
Correct answer: D. The average kinetic energy of the photoelectrons decreases
- A. The maximum kinetic energy of the photoelectrons increases
- B. The minimum kinetic energy of the photoelectrons decreases
- C. The minimum kinetic energy of the photoelectrons increases
- D. The average kinetic energy of the photoelectrons decreases
Explanation
Increasing wavelength lowers frequency because c = fλ, so the photon energy hf decreases. Since maximum kinetic energy is Kmax = hf - Φ, the photoelectrons have lower maximum and average kinetic energy, while the minimum remains approximately zero. Students may choose c by thinking every kinetic-energy value decreases, although the minimum value is already zero.
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About Photons and the Particle Model of Light
The particle model treats light as photons with energy E equals hf and momentum related to wavelength. Questions involve the photoelectric effect, work function, threshold frequency, stopping potential and photon energy, while distinguishing particle behaviour from the wave description of interference and diffraction.
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