The speed of light in vacuum is MCQ with Answer and Explanation

The speed of light in vacuum is
A. 3 × 10⁸ m/s
B. 3 × 10⁴ m/s
C. 3 × 10¹⁰ m/s
D. 3 × 10⁶ m/s
Answer: Option A
Solution (By JKSSB Mock Tests)
c = 2.9979 × 10⁸ m/s, commonly 3×10⁸ m/s. In glass slower. It's a universal constant, maximum speed. Used in relativity, E=mc².

Discuss this Question (0)

No comments yet. Be the first to start the discussion!

Practice More Physics Questions

Question #1
The refractive index of water is 4/3. The speed of light in water is:
A. 3×10⁸ m/s
B. 2.25×10⁸ m/s
C. 1.5×10⁸ m/s
D. 4×10⁸ m/s

Correct Answer: Option B


Explanation:
Refractive index n = c/v, where c = 3×10⁸ m/s (speed in vacuum). Thus v = c/n = (3×10⁸)/(4/3) = 3×10⁸ × 3/4 = 9/4 × 10⁸ = 2.25×10⁸ m/s. This direct formula application is fundamental in optics. Memory aid: 'Higher n ⇒ slower light in medium'. Competitive exams frequently test this calculation with common refractive indices (water 4/3, glass ~1.5). Always use c = 3×10⁸ m/s unless specified otherwise, and ensure unit consistency (m/s here).

This question belongs to: Science Physics
Question #2
The working principle of a hydrogen bomb is
A. Radioactive decay
B. Nuclear fission
C. Nuclear fusion
D. Chemical reaction

Correct Answer: Option C


Explanation:
Hydrogen bomb (thermonuclear weapon) uses uncontrolled nuclear fusion of hydrogen isotopes, triggered by a fission bomb. Releases enormous energy. Sun also uses fusion. Fission used in atomic bomb.

This question belongs to: Science Physics
Question #3
The magnifying power of a simple microscope is maximum when the image is formed at
A. Infinity
B. 2F
C. Near point
D. Focus

Correct Answer: Option C


Explanation:
M = 1 + D/f when image at near point (D = 25 cm). For infinity, M = D/f. So max at near point.

This question belongs to: Science Physics