How long does light take to travel from the Moon to the Earth, a distance of 3.84 x 10^5 km, at 3.00 x 10^8 m/s?

1. First convert the distance to metres: 3.84 x 10^5 km = 3.84 x 10^8 m. 2. Time is distance divided by speed, so t = (3.84 x 10^8 m) divided by (3.00 x 10^8 m/s). 3. The powers of ten cancel, leaving t = 3.84 divided by 3.00 = 1.28 s. 4. The other options all come from mishandling the kilometre to metre conversion by a factor of ten. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.3 The Law of Refraction_