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 Moonís surface. How much is the radius of the lunar orbit around the Earth ?
NCERT Solutions for Class 11 Physics Part 1 Chapter 2 Exercise 29



The radius of the lunar orbit is equal to the distance of the moon from the earth.therefore,
                 r = c*t/2
                   here c = 3×10 raise to power 8
                     t = 2.56 s
              therefore r = 3.84×10 raise to power 8 meter