Physics

The distance of a galaxy is $$56 \times10^{25}m$$. Assume the speed of light to be $$3\times10^8 m s^{-1}$$. Express order of magnitude of time taken by light travelled to the galaxy.


SOLUTION
We know that:

Time taken $$= \dfrac { distance \ travelled }{ speed } $$

So, time taken $$= \dfrac { 56\times { 10 }^{ 25 }m }{ 3\times { 10 }^{ 8 }m{ s }^{ -1 }   } $$

So, the order is $$ {{18.6}\times { 10 }^{ 25-8 }s \  or \ 1.86\times { 10 }^{ 18 }s} $$.
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