Estimate the distance L from which the naked eye can see the light of a laser generating continuous power N = 10 W at a frequency n = 6 • 1014 Hz, if a parabolic mirror with a diameter of D = 50 cm is used to form the beam. The eye sees the source in the green part spectrum if n = 60 quanta per second enter the pupil (pupil diameter d = 5 mm).

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