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## Homework Statement

A speaker emitting sound at a frequency of 20 Hz is moving in the +x direction between two detectors. The speaker is moving at a speed of 30 m/s and the detectors are wired so that they flash red (

**λ**= 700 nm) when the pressure is a maximum and green (

**λ**= 700 nm) when the pressure is a minimum. Use 340 m/s as the speed of sound.

**[1]**Calculate the distance between maxima ahead and behind the moving speaker.

**[2]**Calculate the frequency of the light blinking on each of the detectors.

**[3]**An observer between the detectors is moving at 0.8c in the +x direction. Calculate the frequencies for the red and green lights for each detector this observer sees.

**[4]**Transform the velocity of the speaker to the observer frame as well as the velocity of sound in each direction.

2. Homework Equations

2. Homework Equations

##f' = f \frac{v \pm v_{receiver}}{v \pm v_{source}}##

##t' = \frac{t}{\sqrt{1-\frac{v^2}{c^2}}}##

## The Attempt at a Solution

I am confused at the start with how the detectors detect maximum and minimum pressure and subsequently question1 about the maxima?