Q 2.29: A LASER is a source of very intense, monochromatic, and 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 ?
2.56 s is the total time taken by the LASER to reach Moon and again back Earth.
Time taken by LASER to reach Moon =
We know, Speed of light
The radius of the lunar orbit around the Earth = distance between Earth and Moon =
= Speed of light x Time taken by laser one-way =