What is the approximate speed of light in vacuum?
Difficulty: Hard
About this MCQ
This Hard Everyday Science MCQ checks one syllabus fact. Candidates use it for PPSC Lecturer, FPSC CSS practice.
The question is: “What is the approximate speed of light in vacuum?”
The accepted answer is B. 3 × 10^8 m/s. The speed of light in vacuum (c) is approximately 299,792,458 m/s, commonly approximated as 3 × 10^8 m/s. It is a fundamental constant of nature.
- A. 3 × 10^6 m/s
Why not A: This is far too slow; it is closer to the speed of radio waves in some contexts but not c.
- B. 3 × 10^8 m/s ✓
- C. 3 × 10^10 m/s
Why not C: This overstates the speed of light by two orders of magnitude.
- D. 3 × 10^5 m/s
Why not D: This is roughly the speed of light in km/s misstated as m/s.
Correct answer
B. 3 × 10^8 m/s
Explanation
The speed of light in vacuum (c) is approximately 299,792,458 m/s, commonly approximated as 3 × 10^8 m/s. It is a fundamental constant of nature.
Source: Physics — electromagnetism / relativity constants
Tags: Physics
Relevant exams: PPSC Lecturer, FPSC CSS
Submitted by: MCQsHub Editorial
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