Laser Light Show
Tuesday, August 31st, 2010Laser Light Show
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Consider a pulse of laser light aimed at the moon that bounces back to Earth. The distance between Earth and?
the moon is 3.8 X 10 to the 8 m.
1. Show that the round-trip time for the light is 2.5 seconds.
2. Why does an astronaut on the moon have to be patient in talking with Mission Control on Earth?
Show below.
PART ONE
The speed of light is defined as precisely 299,792,458 meters per second.
Your value for distance to the Moon is *really* general. But I'll use it.
Distance = Rate * Time. We all learned that equation in 6th grade.
Distance to the Moon is given as 3.8E+8 m. Double that distance because it's going there and back, so you have a total of 7.6E+8 m
Solve D=RT for time gives T = D/R input values and see what you get
T = (7.6E+8 m) / (299,792,458 m/s)
T = 2.54 s
PART TWO
He has to be patient because... even if the man at Mission Control answers him *instantly* when he message gets to Earth, it's going to take that minimum round trip of 2.54 s
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where is everybody? not 1 answer?!
