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The distance of a galaxy from Earth is o...

The distance of a galaxy from Earth is of the order of `10^25`m. Calculate the order or magnitude of the time taken by light to reach us from the galaxy.

Text Solution

Verified by Experts

Size of galaxy=`10^25`m
Velocity of light, `c=3 times 10^8 ms^-1`
Time taken by light to reach earth,
`t=10^25/(3times10^8)=1/3times10^17=0.3333times10^17`
While calculating the order of magnitude we will consider the powers of Ten only.
So order of magnitude of time taken by light to reach earth from galaxy is `10^17` seconds.
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