Question

The distance of a galaxy is $56\times {10}^{25}m$. Assume the speed of light to be $3\times {10}^{8}m{s}^{-1}$. Express order of magnitude of time taken by light travelled to the galaxy.

Answer 1

We know that:
Time taken $=\frac{distancetravelled}{speed}$
So, time taken $=\frac{56\times {10}^{25}m}{3\times {10}^{8}m{s}^{-1}}$
So, the order is $18.6\times {10}^{25-8}sor1.86\times {10}^{18}s$.