Physics Alternating Current PMDC Conceptual Practice
PMDC Verified Question 42 of 127
What is the wavelength of a radio wave propagating in free space with a carrier frequency of \(3\text{ kHz}\)?
A
\(10\text{ km}\)
B
\(50\text{ km}\)
C
\(100\text{ km}\)
D
\(1000\text{ km}\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \(100\text{ km}\)
Concept:

The wavelength \(\lambda\) of any electromagnetic wave in free space is the ratio of the speed of light \(c\) to its frequency \(f\).

Formula / Reaction:

$$\lambda = \frac{c}{f}$$

Solution:

  • Given: \(c = 3 \times 10^8\text{ m/s}\), \(f = 3\text{ kHz} = 3 \times 10^3\text{ Hz}\).


  • \(\lambda = \frac{3 \times 10^8}{3 \times 10^3} = 10^5\text{ m} = 100\text{ km}\).


Why other options are incorrect:

  • Opt_A: \(10\text{ km}\) corresponds to \(f = 30\text{ kHz}\).


  • Opt_B: \(50\text{ km}\) corresponds to \(f = 6\text{ kHz}\).


  • Opt_D: \(1000\text{ km}\) corresponds to \(f = 300\text{ Hz}\).

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.

Previous Question All Alternating Current MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App