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Question
The distance of a galaxy is of the order of 1025 m. Calculate the order of magnitude of time taken by light to reach us from the galaxy.
Solution
According to the problem, the distance of the galaxy = 1025 m.
Thus, the required time = `"Distance"/"Speed"`
⇒ `10^25/(3 xx 10^8)` sec
= `1/3 xx 10^17` seconds
Required time = `10/3 xx 10^16`
= 3.33 × 1016 seconds.
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