Question

Ultraviolet light from a distant star is traveling at 3.0 × 108 m/s. How long will it take for the light to reach Earth if it must travel 4.0 × 1013 km?

2.7 × 10–2 hours
2.2 × 103 hours
3.7 × 104 hours
1.3 × 105 hours

Answer 1

Distance = 4.0×10^13 km = 4.0×10^16 m.
Time = distance / speed = (4.0×10^16 m) / (3.0×10^8 m/s) = 1.333...×10^8 s.
Convert to hours: 1.333...×10^8 s ÷ 3600 s/hr ≈ 3.7×10^4 hours.

Answer: 3.7 × 10^4 hours.