1a. Conversations with astronauts on lunar walks had an echo that was used to es

Question

1a. Conversations with astronauts on lunar walks had an echo that was used to estimate the distance to the Moon. The sound spoken by the person on Earth was transformed into a radio signal sent to the Moon, and transformed back into sound on a speaker inside the astronaut’s space suit. This sound was picked up by the microphone in the space suit (intended for the astronaut’s voice) and sent back to Earth as a radio echo of sorts. If the round-trip time was 2.60 s, what was the approximate distance to the Moon, neglecting any delays in the electronics?

Explanation / Answer

The sound spoken by the person on Earth was transformed into a radio signal and then sent to the Moon. Radio signal is an electromagnetic wave and hence travels with a velocity of light, c = 3 * 108 m/s.

The round trip time was t = 2.6 s

Hence, total distance traveled is, D = c * t

D = 3 * 108 m/s * 2.6 s

D = 7.8 * 108 m

But total distance D is twice as the distance(approximate) between Earth and the Moon.

Hence, approximate distance to the Moon is,

d = D /2 = 3.9 * 108 m

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