DOPPLER EFFECT

Doppler effect

An observed change in the frequency (and also wavelength) of a wave when the source or observer is moving (velocity difference)

ultrasonic source example

Describes a sound of a frequency too high to be heard by the normal human ear---above 20,000 hertz RBC becomes the new source and because it's moving towards the receiver, the f of the "new" sound is not the same.. it'll be detected as larger because of doppler effect > the echo from the moving blood is raised in frequency by an amount proportional to blood speed

beat frequency

The difference between the frequencies of the two combining sound waves that make a beat.

if the source moves away from the observer (define as "+" relative velocity), what does the observer perceive?

a decrease in frequency and increase in wavelength

if the observer detects an increase in the wave's frequency, the observer is also detecting what?

a decrease in the wave's wavelength v=(f)(wavelength) --> v/wavelength = f

if the source approaches the observer (defined as "-" relative velocity), what does the observer perceive?

an increase in frequency and decrease in wavelength

does the doppler effect depend on the distance between the observer and the source?

nope

Doppler effect equation

numerator: use + if detector is moving TO source use - if detector is moving AWAY from source denominator: use - if source is moving TO detector (f' decreasing) use + if source is moving AWAY from detector (f' increasing)

doppler effect equation for % change (frequency)

relative frequency > 0 : source away from detector relative frequency < 0 : source & detector are approaching one another

recall that the speed of a wave is set by the MEDIUM, what does this mean for the doppler effect?

that it DOES NOT change the speed of the wave

when you're perceiving the same frequency as what's being emitted,

there's no velocity difference, no doppler effect