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Question
A new unit of length is chosen such that the speed of light in vacuum is unity. What is the distance between the Sun and the Earth in terms of the new unit if light takes 8 min and 20 s to cover this distance?
Solution
Speed of light in vacuum, c = 1 new unit of length s-1
Time taken by light to cover the distance between sun and the earth.
Time taken, t = 8 min 20 s = 500 s
∴ Distance between the Sun and the Earth = c × t
= 1 new unit of length × 500 s
= 500 new units of length
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