• # question_answer Light year is A) Light emitted by the sun in one year.B) Time taken by light to travel from sun to earth.C) The distance travelled by light in free space in one year.  D) Time taken by earth to go once around the sun.

1 light year = speed of light in vacuum x no. of seconds in one year $=(3\times {{10}^{8}})\times (365\times 24\times 60\times 60)$ $=9.467\times {{10}^{15}}m$.