Relative to the radio signals sent out by a spacecraft headed away from the earth,?

Question

the signals that are received on the earth have
a- a lower speed
b- a lower frequency
c- a shorter wavelength
d- all the above properties

Answer 1

d- all of the above

What you are seeing is the Doppler affect. You experience it with a siren (police/ambulance) that is moving. The pitch sounds like it is changing as it approaches then goes past you.

Since the spacecraft is moving away from earth, it's wavelength looks to be stretched, having a longer wavelength, which creates a lower frequency.

Formula's with frequency, wavelength, and wave spped
c = λ × f .............. λ = c / f ............. f = c / λ

c = wave speed
λ = wavelength
f = frequency

The receiving station for the spacecraft has to compensate for the doppler affect.

Answer 2

The correct answer is B. It's not A because light, which a radio signal is, always travels at the speed of light. It's not C because as the spacecraft is heading away from you the wavelength get longer (due to the red shift). So it can't be D.

Answer 3

I guess tht if you wanted to cut fine hairs, you could say the answer is "a", but I am not sure that it really means what you think it means.

The radio signal sent out by the spacecraft travel away from the spacecraft antenna at 186,000 MILES PER SECOND. The spacecraft is moving, it is true, but at a much, much slower rate of speed...maybe like 25,000 - 35,000 MILES PER HOUR. So, the
net effect is not great at all. Signals arriving at earth are still traveling at 186,000 miles per second when they strike the receiving antennas here.

The frequency of the transmitted signals does not change.

The wave length of the transmitted signals does not change.

Answer 4

d i think