Physics Alternating Current PMDC Conceptual Practice
PMDC Verified Question 43 of 127
An electromagnetic wave propagating in vacuum has a frequency of \(6.0\text{ THz}\). What is the total number of complete wavelengths contained within a distance of \(1.0\text{ m}\)?
A
\(2.0 \times 10^1\)
B
\(5.0 \times 10^2\)
C
\(5.0 \times 10^7\)
D
\(2.0 \times 10^4\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \(2.0 \times 10^4\)
Concept:

The number of wavelengths \(N\) in a distance \(d\) is \(N = \frac{d}{\lambda}\), where \(\lambda = \frac{c}{f}\).

Formula / Reaction:

$$N = \frac{d}{\lambda} = \frac{d \cdot f}{c}$$

Solution:

  • Given: \(d = 1.0\text{ m}\), \(f = 6.0\text{ THz} = 6.0 \times 10^{12}\text{ Hz}\), \(c = 3.0 \times 10^8\text{ m/s}\).


  • \(\lambda = \frac{3.0 \times 10^8}{6.0 \times 10^{12}} = 0.5 \times 10^{-4}\text{ m} = 5.0 \times 10^{-5}\text{ m}\).


  • \(N = \frac{1.0\text{ m}}{5.0 \times 10^{-5}\text{ m}} = 2.0 \times 10^4\).


Why other options are incorrect:

  • Opt_A: Off by three orders of magnitude.


  • Opt_B: Calculation error from incorrect metric prefix conversion.


  • Opt_C: \(5.0 \times 10^7\) represents an inverted frequency/speed calculation.

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