question 25 A television reception antenna. has cross wires of various lengths t

Question

question 25

A television reception antenna. has cross wires of various lengths to most efficiently receive different wavelengths. 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? Lunar astronauts placed a reflector on the Moon's surface off which a

Explanation / Answer

If we suppose that the radio signal is travelling with the speed of light in outer space (appx 300000 km/s) we can find the distance by: s=u*t

t is half of round-trip time, so

s=300000*1.3=390000 km. The distance drom earth to moon is 370300 km, so this is a good approxiamtion.

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