Question

The distance of a galaxy is 5·6 × 10²⁵ m . Assuming the speed of light to be 3 × 10⁸ ${\displaystyle {\text{ms}}^{-1}}$. Find the time taken by light to travel this distance . 
[Hint : ${\displaystyle \text{Time taken}=\frac{\text{Distance travelled}}{\text{speed}}}$]

Answer 1

Distance of galaxy = 5.6 × 10²⁵ m

Speed of light = 3 × 10⁸ m/s

${\displaystyle \text{Time taken by light}=\frac{\text{Distance travelled}}{\text{speed of light}}}$

= ${\displaystyle \left(\frac{5.6\times {10}^{25}}{3\times {10}^8}\right)}$ s

= 1.87 × 10¹⁷ s