Question

Define light year and astronomical unit.
[2 marks]

Answer 1

Light year - A light year is the distance light travels in one year.

$1Ly=9.46\times {10}^{15}m$
[1 mark]

Astronomical unit - An astronomical unit is the average distance between the earth and the sun.
$1AU=1.5\times {10}^{11}m$
[1 mark]