Question

If the light travels at a speed of 3.0 ×10^5 km per second,the light from a star which is 8.1×10^3 km away from the earth takes __ to reach the surface of the earth

Answer 1

Answer:

3.0 multiply by 8.1

3.0 multiply by 8.1 = 5.4

Answer 2

Answer:

The time taken by light from star to reach the earth is 0.027 sec

Step-by-step explanation:

Given as :

The distance between light from star to earth = d = 8.1 × $10^{3}$  km

The speed of light from star to earth = s = 3 × $10^{5}$ km/s

let The time taken by light from star to reach the earth = t sec

According to question

Time = $\dfrac{Distance}{Speed}$

or, t = $\dfrac{d}{s}$

Or, t = $\dfrac{8.1\times 10^{3}}{3\times 10^{5}}$

Or, t = 2.7 × $10^{3-5}$

∴   t = 2.7 × $10^{-2}$ sec

So, The time taken by light from star to reach the earth = t = 0.027 sec

Hence, The time taken by light from star to reach the earth is 0.027 sec Answer