One light year is equal to________________?
Correct answer: A. 9.5 x 10^15m
- A. 9.5 x 10^15m
- B. 9.5 x 10^15sec
- C. 9.5 x 10^15Km
- D. 9.5 x 10^15cm
Explanation
A light-year is a distance, not a time: 1 light-year = speed of light × 1 year = (3.00 x 10^8 m s-1)(3.156 x 10^7 s) ≈ 9.46 x 10^15 m, rounded to 9.5 x 10^15 m. Students may choose B because the word year suggests seconds, but a light-year measures how far light travels in one year.
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