Calculating Frequency of Star's Radio Signals from Earth

[crosbykins]

Homework Statement

A distant star has been measured as moving at a speed of 0.8c away from Earth. If a planet of this star sends radio signals to Earth once every second (according to their time scale), how often would we receive them (according to out time scale)?

Homework Equations

Δts = Δtm/ √(1 – (v^2/c^2)

The Attempt at a Solution

Δts = Δtm/ √(1 – (0.8c)^2/c^2)
= 1/ √(1 – (0.8c)^2/c^2)
= 2.24 s

f = 1/2.24 s
= .45 signal/second

Therefore, we would receive .45 signal/second

*does this look ok?

 

[tiny-tim]

hi crosbykins!

have you taken account of the fact that the distance each signal has to travel is increasing?