Relative to the radio signals sent out by a spacecraft headed away from the earth, the signals that are received on the earth have
A) a lower speed.
B) a lower frequency.
C) a shorter wavelength.
D) all of these properties.

Question

Quizplus · Accepted Answer

According to the Doppler Effect, when a source of waves is moving away from the observer, the frequency of the waves detected by the observer decreases. This means that the radio signals sent by the spacecraft will have a lower frequency when received on Earth. The speed of the signals depends on the speed of light and remains constant. The wavelength of the signals is inversely proportional to frequency, so if the frequency is lower, the wavelength will be longer, not shorter. Therefore, only option B is correct.

Relative to the Radio Signals Sent Out by a Spacecraft