Task id12087

In the Soviet-French experiment on optical location of the Moon, pulsed radiation from a ruby laser at a wavelength of L = 0.69 μm was directed using a telescope with a mirror diameter of D = 2.6 m onto the lunar surface. A reflector was installed on the Moon, which worked like an ideal mirror with a diameter of d = 20 cm, reflecting light exactly in the opposite direction. The reflected light was captured by the same telescope and focused on a photodetector. Complete the following tasks and answer the questions: 1. With what accuracy should the optical axis of the telescope be set in this experiment? 2. Neglecting light losses in the Earth’s atmosphere and in the telescope, estimate what fraction of the laser light energy will be recorded by the photodetector after reflection from the Moon. 3. Is it possible to see the reflected light pulse with the naked eye if the threshold sensitivity of the eye is taken equal to n=100 light quanta, and the energy emitted by the laser during the pulse is equal to E=1 J? 4. Evaluate the gain that comes from using a reflector. Assume that the surface of the Moon scatters a = 10% of the incident light uniformly into a solid angle of 2n steradians. Notes The distance from the Earth to the Moon is L=380 thousand km. The diameter of the pupil of the eye is taken equal to dzr = 5 mm. Planck's constant h=6.6•10-34 J•s.