(II) A light-year is the distance light travels in one year (at speed = 2.998 X 108 m/s)(a) How many meters are there in 1.00 light-year? (b) An astronomical unit (AU) is the average distance from the Sun to Earth. 1.50 X 108 km How many AU are there in 1.00 light-year?

Solution: 22P

Step 1 of 3</p>

(A) Speed of light C = 2.998 x 108 m/s

Hence 1 light year = ( 2.998x108 m/s)(3.156 x 107 s)

1.00 light year = 9.46 x 1015 m

Therefore 1.00 light year = 9.46 x 1015 (The least number of significant figures is 3 as given

in 1.00 light year, so the answer should have maximum 3 significant figures)

Step 2 of 3</p>

(B) 1AU = 1.5 x 108 km

= 1.5 x 108 x 1000 m (As 1 km = 1000 m)

= 1.5 x 1011m

Hence 1.00 light year = 6.31 x 104 AU