(a) The distance to a star is approximately 4.50 1018 m. If this star were to bu

Question

(a) The distance to a star is approximately 4.50 1018 m. If this star were to burn out today, how long from now would we see it disappear? _______years

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

(c) How long does it take for a microwave radar signal to travel from the 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 10.3 km away? ____________s

Explanation / Answer

Here,

a) distance , d = 4.5 *10^18 m

time taken for star to disappear = distance/speed

time taken for star to disappear = 4.5 *10^18/(3 *10^8) s

time taken for star to disappear = 1.5 *10^10 s

time taken for star to disappear = 475.6 years

b)

time taken = distance /speed

time taken = 227.9 *10^9/(3 *10^8) s

time taken = 759.7 s = 12.66 min

c)

time taken = 2 * distance between earth and moon/speed

time taken = 2 * 370300 *10^3/(3 *10^8)

time taken = 2.47 s

time taken for a microwave radar signal to travel from the Earth to the Moon and back is 2.47 s

d)

time taken = distance /speed

time taken = 2pi * 6371 *10^3/(3 *10^8)

time taken = 0.133 s

time it take for a radio wave to travel once around the Earth in a great circle, close to the planet's surface is 0.133 s

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