Question

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

• A. $0.87\times {10}^{18}s$
• B. $1.87\times {10}^{18}s$
  
• C. $18.7\times {10}^{18}s$
• D. $1.87\times {10}^{17}s$

Answer 1

The correct option is B $1.87\times {10}^{18}s$

$time=distance/speed$

$\Rightarrow time=\frac{56\times {10}^{25}}{3\times {10}^8}$

$\Rightarrow time=18.7\times {10}^{17}=1.87\times {10}^{18}s$