The Apollo 11 astronauts set up a panel of efficient corner-cube retro reflector
ID: 2243379 • Letter: T
Question
The Apollo 11 astronauts set up a panel of efficient corner-cube retro reflectors on the Moon's surface (see figure below). The speed of light can be found by measuring the time interval required for a laser beam to travel from the Earth, reflect from the panel, and return to the Earth. Assume this interval is measured to be 2.51 s at a station where the Moon is at the zenith and take the center-to-center distance from the Earth to the Moon to be equal to 3.84 Times 108 m. (The Moon's radius is 1.74 Times 106 m, and the Earth's radius is 6.37 Times 106m.)Explanation / Answer
A) Distance covered by light = 2*(center to center distance from the Earth-radius of Earth-radius of moon)
==> D= 2*(3.84E8- 1.74E6 - 3.67E6) = 2*3.786E8 m
and time= 2.51 sec
==> speed of light = 2*3.786E8/2.51 = 3.0167 E8 m/s
B) yes it neccesery to consider the size of earth and moon
because light travels from one surface to other surface
not center to center
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