A LASER is a source of very intense, monochromatic, and the unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth ?

Asked by Abhisek | 1 year ago | 194

Time taken for the laser beam to return to Earth after reflection by the Moon’s surface = 2.56 s

The speed of laser light ,c = 3 x 10^{8 }m/s.

Let d be the distance of Moon from the Earth,

The time taken by laser signal to reach the Moon, t = \( \dfrac{2d}{c}\)

Therefore, d =\( \dfrac{tc}{2}\) = \(
\dfrac{ (2.56 \times 3 \times 10^8)}{2}\) = 3.84 x 10^{8} m

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