Physics Dawn of Modern Physics SZABMU 2023
PMDC Verified Question 19 of 52
Red light is used in photographic dark room because of:
A
Low frequency, long wavelength
B
High frequency, short wavelength
C
Low frequency, short wavelength
D
High frequency, long wavelength
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Low frequency, long wavelength
Concept:

To prevent the unwanted exposure of photosensitive chemicals, ambient light must consist of photons that lack the threshold energy required to initiate the chemical reaction.

Formula:

$$ E = hf = rac{hc}{\lambda} $$

Solution:

  • Energy is directly proportional to frequency and inversely proportional to wavelength.


  • Red light sits at the lower-frequency end of the visible spectrum.


  • It inherently possesses a Low frequency and long wavelength, meaning its photons carry minimal energy.


Why other options are incorrect:

Options with high frequency or short wavelength describe energetic light (like blue or UV) which would instantly expose and ruin undeveloped film.

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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