Physics Waves NUMS 2022
PMDC Verified Question 74 of 125
Crest of a wave acts as:
A
Concave lens
B
Convex lens
C
Convex mirror
D
Plane mirror
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Convex lens
Concept:

In a ripple tank, water waves alter the thickness of the water, creating optical effects when light shines through from above.

Solution:

  • A wave crest is a localized region where the water is deeper and bulges outward.


  • This physical shape perfectly mimics a converging glass lens. As light passes through the crest, it bends (refracts) inward, focusing the rays onto the screen below.


  • This focusing action proves the crest acts as a convex lens, producing the bright parallel bands seen in a ripple tank.


Why other options are incorrect:

A wave trough acts as a concave lens (diverging light to make dark bands). Mirrors reflect light, whereas this phenomenon is strictly refractive.

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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