a) The distance to a star is approximately 4.30 x 10^18 m. If this star were to

Question

a) The distance to a star is approximately 4.30 x 10^18 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 Venus?
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 9.6 km away?
s

Explanation / Answer

speed of light = 3e8 m/sec

a) time = distance/speed = 4.3e18/3e8 = 1.433e10 sec = 454.2 years

b) distance of sun and venus = 1.08e11m

time = 1.08e11/3e8 = 360 sec = 6 minuts

c) Distance of moon to earth = 3.844e8 m

time = 2*3.844e8/3e8 = 2.563 sec

d) earth radius = 6.371e6 m

circumference = 2*pi*r = 4e7 m

time = 4e7/3e8 = 0.1333 sec

e) time = 9.6e3/3e8 = 3.2e-5 sec

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