Question

A. The distance to a star is approximately 8.58 ✕ 10^18 m. If this star were to burn out today, in how many years would we see it disappear?
b. How long does it take sunlight to reach Earth?
c. How long does it take for a microwave radar signal to travel from Earth to the Moon and back?

Answer 1

Answer:

906.27931 years

8.34 minutes

2.56266 seconds

Explanation:

v = Velocity of light = $3\times 10^8\ m/s$

s = Distance

Time is given by

$t=\dfrac{s}{v}\\\Rightarrow t=\dfrac{8.58\times 10^{18}}{3\times 10^8\times 365.25\times 24\times 3600}\\\Rightarrow t=906.27931\ years$

We would see the star disappear after 906.27931 years after it actually disappeared.

Distance between Earth and Sun = 150.18 billion m

$t=\dfrac{150.18\times 10^9}{3\times 10^8\times 60}\\\Rightarrow t=8.34\ minutes$

It takes 8.34 minutes for sunlight to reach Earth.

Distance between Earth and Moon = 384.4 million m

$t=\dfrac{2\times 384.4\times 10^6}{3\times 10^8}\\\Rightarrow t=2.56266\ s$

It takes 2.56266 seconds for a microwave radar signal to travel from Earth to the Moon and back.