# Apparent frequency of reflected wave

1. Aug 3, 2014

### desmond iking

1. The problem statement, all variables and given/known data

A police car P with its siren on is chasing car T . The frequency of the siren is 1000hz. The speed of police car P is 30m/s . and the speed of car T is 40m/s . What's the apparent frequency of the siren heard by driver T > the ans is 967hz . I managed to get the ans for this.
But i didnt managed to get the ans for part b .
here's part b :
What's the apparent frequency of the reflected wave heard by driver T ? the ans is 941 hz. p/s : i assume both P and T are moving to the right.

2. Relevant equations

3. The attempt at a solution
apparent frequency of the siren heard by driver T = ((330-40)/(330-30))x 1000 = 967hz.

b ) apparent frequency of the siren emitted by P to the left = (330/(330+30)) x 1000 = 917hz.

apparent frequency of the siren reflected from the right and heard by T after reflection = ((330-40) / (330-30) ) x 917hz = 886hz . i am not sure which direction of the sound wave is reflected. can somoene explain on this?

2. Aug 3, 2014

### vela

Staff Emeritus
Are you sure the question is asking about driver T hearing the reflected wave? It makes more sense that driver P hears the wave reflected off of T.

3. Aug 3, 2014

### desmond iking

yes the question asking T heard the wave

4. Aug 3, 2014

### HallsofIvy

Staff Emeritus
Driver T can't hear the reflected wave- it is moving away from him.

5. Aug 4, 2014

### desmond iking

so is the question wrong?

6. Aug 4, 2014

### vela

Staff Emeritus
Sounds like it. Try calculating the frequency P hears for the reflected wave.