Physics Dawn of Modern Physics UHS 2023
PMDC Verified Question 16 of 52
In Compton effect, a photon of a certain wavelength collides with a stationary electron. The wavelength of the emitted photon is:
A
Shorter
B
Longer
C
Same
D
Infinite
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Longer
Concept:

Compton scattering dictates that an incident photon loses energy when it collides with a stationary electron.

Formula:

$$ \lambda_{scattered} - \lambda_{incident} = \frac{h}{m_ec}(1-\cos\theta) $$

Solution:

  • Because the photon transfers kinetic energy to the electron, its own final energy decreases.


  • Energy and wavelength are inversely proportional (\( E = \frac{hc}{\lambda} \)).


  • A decrease in energy guarantees an increase in wavelength. Thus, the emitted (scattered) photon has a strictly longer wavelength.


Why other options are incorrect:

A shorter wavelength would imply the photon magically gained energy from nowhere. "Same" implies a perfectly elastic collision with no energy transfer, which does not happen.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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