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

Q. 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 ?

Q. In a Young's double slit experiment a monochromatic laser beam is used to provide the coherent source. To emit the monochromatic laser beam electron has to jump through an energy band of energy difference $4.2eV$ inside the laser. The wavelength of the laser beam emitted by the laser source is ___ $\dot{A}$.

Q. Assertion :A laser beam of $0.3W$ can drill a hole through metal sheet, whereas light of $1000W$ can not do so Reason: Laser beam has very high frequency

Q. A robot sent to the moon sends a laser light towards the earth. If it takes $13$ seconds to reach the earth then calculate the distance between moon and the earth in kilometres.
(Given : Velocity of light is $3\times {10}^{8}m/s$)

Q. Which of the following properties of laser beam can be used to measure long distances?