Question

The distance of a galaxy is 5.4 × 1025 m. Assuming the speed of light to be 3 × 108 ms–1, find the time taken by light to travel this distance.

Answer 1

Time taken by light to reach the given galaxy = 18 * 10^16 seconds

Explanation:

The distance of a galaxy is 5.4 X 10^25 m.

Speed of light = 3 * 10^8 ms-1​.

We need to find the time taken by light to travel this distance.

Time taken = Distance travelled / speed

Substituting, we get time =  5.4 X 10^25 / 3 * 10^8 = (5.4 / 3) * 10^17 = 1.8 * 10^17 seconds

Time taken by light to reach the given galaxy = 18 * 10^16 seconds