Question

Light year is used to measure

• A. distance between stars
• B. distance between atoms
• C. revolution time of earth around sun
• D. none of the above

Answer 1

Answer: (A)

distance between stars

Answer 2

Light year is an important unit of long distances (to measure the distance of stars, and terrestrial objects). One light year is the distance traveled by light in a vacuum in one year.

As velocity of light in vacuum is $3 \times 10^{8} ms ^{-1}$ and $1$ year $=365 \times 24 \times 60 \times 60$ second,

Therefore, 1 light $=3 \times 10^{8} \times(365 \times 24 \times 60 \times 60)$ metre

$\therefore 1$ light year $=9.46 \times 10^{15} m$

A light-year is a measurement of distance and not time (as the name might imply). A light-year is a distance a beam of light travels in a single Earth year, which equates to approximately 6 trillion miles (9.7 trillion kilometers).