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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.
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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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