Question

A light year is the distance travelled by light in one year. How many kilometers does light travel in a year assuming speed of light is $3\times {10}^{8}m{s}^{-1}$ ?

• A. 9.56 trillion kilometers
• B. 9.46 trillion kilometers
• C. 9.36 trillion kilometers
• D. 9.26 trillion kilometers

Answer 1

The correct option is B 9.46 trillion kilometers

$Distance=Speed\times Time$
The speed of light = $3\times {10}^{8}m{s}^{-1}$
Number of seconds in a year = $3.154\times {10}^7$ seconds.
Therefore, distance travelled by light in 1 year (in kilometres) =
=$\frac{(3\times {10}^{8}m{s}^{-1}\times 3.154\times {10}^7)}{1000}$

=$9.46\times {10}^{12}kms$
=$9.46trillionkilometres$