Using the Apache Point Observatory Lunar Laser-Ranging Operation (Fig. P23.61, page 822), the distance to the Moon
Question:
Using the Apache Point Observatory Lunar Laser-Ranging Operation (Fig. P23.61, page 822), the distance to the Moon is determined by how long it takes for a laser pulse to travel from the Earth to the Moon and then reflect back to the Earth from special reflector arrays placed there by the Apollo astronauts. A 2.3-W laser sends 20 pulses per second (each only 100 picoseconds long) at a wavelength of 532 nm. Due to atmospheric absorption and dispersion of the beam, only a very faint reflected pulse arrives back at the observatory with a power of 3.0x10-17 W.
(a) How many photons does the observatory send in an outgoing pulse?
(b) How many photons are received in a returning pulse?
(c) How many photons are sent for every one that is detected upon return?
Figure P23.61
Step by Step Answer:
College Physics Reasoning and Relationships
ISBN: 978-0840058195
2nd edition
Authors: Nicholas Giordano