A source emits waves of constant frequency. An observer detects a different frequency.

A galaxy is moving away from Earth at a speed much smaller than the speed of light.

A point source of sound moves to the right through still air. Wavefronts are closer together on the right of the source than on the left.

A star moves across the sky with velocity perpendicular to the line joining it to Earth. In the low-speed Doppler treatment, what is the expected Doppler shift of its spectral lines?

The same absorption-line pattern from hydrogen is observed in a galaxy spectrum at wavelengths longer than the laboratory wavelengths.

A source of sound is stationary in still air. An observer moves directly towards the source.

A sound source moves directly away from a stationary observer through still air.

A stationary sound source emits frequency $f$. An observer moves towards the source with speed $u_o$ through still air. The speed of sound is $v_w$.

In Doppler ultrasound, the ultrasound beam makes an angle $heta$ to the direction of blood flow.

An astronomical spectrum shows a familiar pattern of absorption lines shifted as a whole.

A spectral line with laboratory wavelength 500.00 nm is observed at 500.05 nm from a star. The speed of light is $3.00 imes10^8\, ext{m s}^{-1}$.

A rotating star has one edge moving towards Earth and the opposite edge moving away.

A sound source of frequency 500 Hz moves directly towards a stationary observer at $20\, ext{m s}^{-1}$. The speed of sound is $340\, ext{m s}^{-1}$.

A stationary source emits sound of frequency 400 Hz. An observer moving towards the source detects 408 Hz. The speed of sound is $340\, ext{m s}^{-1}$.

Why is the approximate Doppler frequency shift in medical ultrasound reflected from moving blood cells proportional to $2u$ rather than $u$?

A sound source approaches a stationary observer with speed $u_s$ in a medium where the sound speed is $v_w$. According to $f'=f\left(v_w/(v_w-u_s)\right)$, what happens as $u_s$ approaches $v_w$ from below?

A source of sound moves at constant speed through still air.

A spectral line has laboratory wavelength $656.3\, ext{nm}$. It is observed from a star at $656.0\, ext{nm}$. Use $c=3.00 imes10^8\, ext{m s}^{-1}$.

Compare the Doppler effect for sound in air with the Doppler effect for light in a vacuum.

The approximation $\Delta f/f\approx v/c$ is often used for light.

A whistle emits sound of frequency 720 Hz while moving directly away from a stationary observer at $18\, ext{m s}^{-1}$. The speed of sound is $340\, ext{m s}^{-1}$.

A stationary alarm emits sound of frequency 1000 Hz. A cyclist moving directly away from the alarm detects a frequency of 970 Hz. The speed of sound is $330\, ext{m s}^{-1}$.

A sound source moves away from a stationary observer.

The graph shows fractional frequency shift $\Delta f/f$ for light from laboratory sources moving directly towards a detector at different speeds.

A ripple source moves across water. A photograph of the wavefronts is shown.

A police radar emits microwaves of frequency $24.0\, ext{GHz}$. A car moves directly towards the radar at $25.0\, ext{m s}^{-1}$. Use $\Delta f\approx 2vf/c$ with $c=3.00 imes10^8\, ext{m s}^{-1}$.

Light from a rotating star is observed from Earth.

Redshift measurements can be used to estimate distances to distant galaxies.

A moving sound source and a moving sound observer can both produce Doppler shifts.

A Doppler ultrasound probe emits ultrasound of frequency $5.0\, ext{MHz}$. The reflected signal from blood has a frequency shift of $5.0\, ext{kHz}$. The speed of ultrasound in tissue is $1540\, ext{m s}^{-1}$ and the beam is at $60^\circ$ to the flow.

Use $\Delta f/f\approx 2u\cos heta/v_w$.

A radar emits microwaves of frequency $24.0\, ext{GHz}$. The reflected signal from a vehicle has a frequency shift of $3.20\, ext{kHz}$. The vehicle moves directly along the radar beam. Use $c=3.00 imes10^8\, ext{m s}^{-1}$.

In Doppler ultrasound, an error is made in estimating the angle between the ultrasound beam and the blood-flow direction.

The table shows laboratory wavelengths and observed wavelengths for three absorption lines in the spectrum of a galaxy.

A table gives redshift-derived recessional speeds and independently estimated distances for several galaxies.

A source of sound of constant emitted frequency moves directly towards a stationary microphone at different speeds. The speed of sound is known.

A stationary radar records frequency shifts from three vehicles moving directly along the radar beam.

A stationary observer detects a sound frequency of 430 Hz from a source emitting 400 Hz. The source moves directly towards the observer through still air. The speed of sound is $340\, ext{m s}^{-1}$.

The diagram shows the measured wavelength of the same spectral line from different positions across the disk of a rotating star.

A Doppler ultrasound system measures the frequency shift from blood flowing at the same speed while the probe angle is varied. The graph shows $\Delta f$ against $\cos heta$.

A stationary loudspeaker emits a constant frequency. A microphone moves directly towards the loudspeaker at different speeds. The graph shows observed frequency against microphone speed.

A police siren is heard by a stationary pedestrian as a police car approaches and then passes.

A sound source and a sound observer may move relative to the air.

Two experiments use the same sound frequency and the same speed of sound. In experiment X the source moves towards a stationary detector. In experiment Y the detector moves towards a stationary source. The table gives observed frequency for the same set of speeds.

Spectroscopy is used to investigate the motion of a distant galaxy. A laboratory spectral line at $486.1\, ext{nm}$ is observed at $489.0\, ext{nm}$ in the galaxy spectrum.

A star of radius $7.0 imes10^8\, ext{m}$ rotates. A spectral line of laboratory wavelength $600.0\, ext{nm}$ is observed from one limb at $599.94\, ext{nm}$ and from the opposite limb at $600.06\, ext{nm}$.

A sound source emits frequency 600 Hz in still air where the sound speed is $340\, ext{m s}^{-1}$.

A Doppler ultrasound probe sends waves of frequency $4.0\, ext{MHz}$ into tissue. The speed of ultrasound in the tissue is $1540\, ext{m s}^{-1}$. The beam is at $30^\circ$ to the blood-flow direction and the measured reflected frequency shift is $7.2\, ext{kHz}$.

Doppler radar and Doppler sound measurements are both used to determine speeds.

An ambulance siren emits sound at 900 Hz. A stationary observer hears 960 Hz as the ambulance approaches. Take the speed of sound as $340\, ext{m s}^{-1}$.