(a) How long in seconds does it take a radio signal to travel 130 km from a tran
ID: 1561480 • Letter: #
Question
(a) How long in seconds does it take a radio signal to travel 130 km from a transmitter to a receiving antenna? (b) We see a full Moon by reflected sunlight. How much earlier did the light that enters our eye leave the Sun? The Earth-Moon and Earth-Sun distances are 3.8 times 10^5 km and 1.5 times 10^8 km, respectively. (c) What is the round-trip travel time in seconds for light between Earth and a spaceship at a 7.9 times 10^9 km distance from Earth? (d) Suppose astronomers observe a supernova about 5700 light-years (Iy) distant. How long ago in years did the explosion actually occur? (a) Number 4.333E-4 Units s (b) Number 501.266 Units s (c) Number 52666.6 Units s (d) Number 3683 Units yearsExplanation / Answer
d)
distance = 5700 light years = 5700 (9.46 x 1015) m
speed of light = 3 x 108 m/s
t = time taken by the light = distance / speed
t = 5700 (9.46 x 1015) / (3 x 108)
t = 179740 x 106 sec
t = (179740 x 106 ) (1/(365 x 24 x 3600)) yrs
t = 570o yrs
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