What is the approximate speed of light in vacuum?
Difficulty: Hard
About this MCQ
This Hard Everyday Science question asks: What is the approximate speed of light in vacuum? The correct choice is B. 3 × 10^8 m/s. Read the options below, commit to one, then use the explanation to see why that choice holds and why the others do not.
Everyday Science items like this one are written for Pakistan exams such as CSS, FPSC, PPSC, and NTS. The difficulty label is a hint about how much of the topic the stem assumes, not a score. Tags and exam names, when they are present, tell you where else the same idea is tested. Previous and next links stay in Everyday Science so you can continue the subject. Related questions point at nearby stems if you want another angle on the same idea.
Treat the explanation as part of the question, not a footnote. If you missed it, reread the stem against the correct option before you open the next Everyday Science item. A timed quiz is the same pool with a clock and a score. A past paper is a full sitting rather than this single question.
- 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
3 × 10^8 m/s is the value that answers “What is the approximate speed of light in vacuum” (option B). Option A (3 × 10^6 m/s) is wrong: This is far too slow; it is closer to the speed of radio waves in some contexts but not c. Option C (3 × 10^10 m/s) is wrong: This overstates the speed of light by two orders of magnitude. Option D (3 × 10^5 m/s) is wrong: This is roughly the speed of light in km/s misstated as m/s. Keep 3 × 10^8 m/s as the Everyday Science fact for this stem.
Source: Physics — electromagnetism / relativity constants
Tags: Physics
Relevant exams: PPSC Lecturer, FPSC CSS
Submitted by: MCQsHub Editorial
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