(a) The distance to a star is approximately 7.60 1018 m. If this star were to bu

Question

(a) The distance to a star is approximately 7.60 1018 m. If this star were to burn out today, in how many years would we see it disappear?
years

(b) How long does it take for sunlight to reach Jupiter?
minutes

(c) How long does it take for a microwave radar signal to travel from Earth to the Moon and back?
s

(d) How long does it take for a radio wave to travel once around the Earth in a great circle, close to the planet's surface?
s

(e) How long does it take for light to reach you from a lightning stroke 8.3 km away?
s

Explanation / Answer

d = 7.60*1018 m. c = 3.00*108 m/s

time t = d/c = 2.53*1010 s = 803 years

(b) How long does it take for sunlight to reach Jupiter?

d = 7.79*1011 m. c = 3.00*108 m/s

time t = d/c = 2.53*1010 s = 2597 s = 43.3 minutes

(c) How long does it take for a microwave radar signal to travel from Earth to the Moon and back?

d = 3.84*108 m. c = 3.00*108 m/s

time t = 2d/c = 2.56 s

(d) How long does it take for a radio wave to travel once around the Earth in a great circle, close to the planet's surface?

d = 2*6.38*108 m. c = 3.00*108 m/s

time t = d/c = 13.3 s

(e) How long does it take for light to reach you from a lightning stroke 8.3 km away?

d = 8.3*103 m. c = 3.00*108 m/s

time t = d/c = 2.77*10-5 s

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