Light year is unit of: MCQ with Answer and Explanation

Light year is unit of:

A. Luminosity

B. Time

C. Distance

D. Speed

Answer: Option C

Solution (By JKExamLibrary)

Light year: distance light travels in one year in vacuum ≈ 9.46×10¹⁵ m. Astronomical distance unit, not time. Memory aid: 'Light year = speed × time = distance'. Unit knowledge frequently tested in competitive exams to avoid common misconception about light year being time unit.

This question belongs to: Science Physics

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Question #1 Report Error

A ray of light passes from air to glass (refractive index 1.5). If angle of incidence is 30°, angle of refraction is (sin30=0.5)

A. 45°

B. 60°

C. 30°

D. 19.47°

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Correct Answer: Option D

Explanation:
Snell's law: n₁ sin i = n₂ sin r. 1×0.5 = 1.5 sin r => sin r = 0.5/1.5 = 1/3 ≈ 0.3333 => r ≈ 19.47°. So A.

This question belongs to: Science Physics

Question #2 Report Error

Frequency of sound wave determines:

A. Speed

B. Timbre

C. Pitch

D. Loudness

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Correct Answer: Option C

Explanation:
Frequency → pitch perception: higher frequency = higher pitch. Loudness depends on amplitude; timbre on waveform; speed on medium properties. Memory aid: 'Frequency = pitch; Amplitude = loudness'. Basic sound property question frequently tested to verify perceptual attribute associations in competitive exams.

This question belongs to: Science Physics

Question #3 Report Error

The material used for making solar cells is

A. Aluminium

B. Iron

C. Silicon

D. Copper

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Correct Answer: Option C

Explanation:
Silicon semiconductor, abundant, efficient for photovoltaic cells. Also gallium arsenide. Solar cells convert light to electricity. Renewable energy technology.

This question belongs to: Science Physics

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