Physics Dawn of Modern Physics BUMHS 2024
PMDC Verified Question 12 of 52
In photo-electric effect electrons are emitted on incidence of light upon certain material surfaces:
A
Below a certain frequency
B
Beyond a certain wavelength
C
Above a certain frequency
D
None of the given options
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Above a certain frequency
Concept:

A binding energy barrier (work function) exists for electrons in a metal, requiring a minimum packet of incident energy to overcome.

Formula:

$$ hf \geq \Phi $$

Solution:

  • Since energy scales directly with frequency, a threshold frequency (\( f_0 \)) exists.


  • Light must possess a frequency strictly above this \( f_0 \) limit to provide enough individual photon energy to eject an electron.


Why other options are incorrect:

"Below a certain frequency" provides insufficient energy. "Beyond a certain wavelength" implies longer wavelengths, which means lower frequencies and lower energy, defeating emission.

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