The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
A common example of Doppler shift is the change of pitch heard when a vehicle sounding a horn approaches and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.The reason for the Doppler effect is that when the source of the waves is moving towards the observer, each successive wave crest is emitted from a position closer to the observer than the crest of the previous wave. Therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrivals of successive wave crests at the observer is reduced, causing an increase in the frequency. While they are traveling, the distance between successive wave fronts is reduced, so the waves "bunch together". Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wave fronts is then increased, so the waves "spread out".
For waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source are relative to the medium in which the waves are transmitted. The total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium. Each of these effects is analyzed separately. For waves which do not require a medium, such as electromagnetic waves or gravitational waves, only the relative difference in velocity between the observer and the source needs to be considered, giving rise to the relativistic Doppler effect.
Homework Statement
A siren has two loud speakers attached to a rotating disk. The disks radius is 3m. The speakers emit a sound frequency of 300 Hz.(Speed of sound in air is 344 m/s)
A)How fast does the disk need to spin for an observer standing some distance away to perceive two frequencies...
Was it considered that the force of gravity could vary according to the redshift equation?
1+z=\frac{1+v \cos (\theta)/c}{\sqrt{1-v^2/c^2}}
If those who consider this are right, then it would imply that an object leaving a gravitational system would experience a slight decrease in the...
I have a question about of light waves. Moving at high speeds toward or away from visible light could be the difference of experiencing that light as violet or red. Of course this experience is due to the photoreceptors in the eye seemingly experiencing a shorter or longer wavelength. My...
Homework Statement
My books states, considering a stationary source emitting waves at frequency f, such waves having velocity v, and an observer approaching the source along a linear path at velocity vO we have that: The observer registers the velocity of the waves at v+v0. Up until now all...
Hi,
I'm reading "The First Three Minutes" by Steven Weinberg
And am confused about this paragraph...
"Astronomers are able to measure the motion of a luminous body in a direction directly along the line of sight much more accurately than they can measure its motion at right angles to...
Im trying to solve back for Jupiters effect on the suns orbital velocity. I've looked up the asnwer and its 12.7 m/s
and the formula I have for this is
http://en.wikipedia.org/wiki/Doppler_spectroscopy
v = SQR (Gm*/r)
where G is Grav constant
M is the mass of the star (planets mass is...
Homework Statement
Two cars traveling with the same speed move directly away from one another. One car sounds a horn whose frequency is 185 Hz and a person in the other car hears a frequency of 173 Hz. What is the speed of the cars?
Homework Equations
The Doppler Effect.
The...
Homework Statement
A star is moving away from Earth at a speed of 2.4 x 10^8 m/s. Light of wavelength 480 nm is emitted by the star. What is the wavelength as measured by an Earth observer?Homework Equations
fo=fs(1 - vrel/c)
I substracted because they the star is moving away from the earth...
Homework Statement
Not really a homework, but i did run across it while attempting some questions. Was reading through the derivations of relativistic doppler effect on EM waves and was reading wiki(http://en.wikipedia.org/wiki/Relativistic_Doppler_effect" when i came across something...
The problem:
I have to answer a question about the Doppler effect using the formula attached.
I know i have to solve for Vw, but I get
Vw/Vw=(Fd/Fs)(-Fs)
and I am possitive that's not right, can someone please help me out??
Thankyou
A stationary destroyer is equipped with sonar that sends out pulses of sound at 30.000 MHz. Reflected pulses are received from a submarine directly below with a time delay of 60 ms at a frequency of 29.958 MHz.
(a) If the speed of sound in seawater is 1.55 km/s, find the depth of the...
Homework Statement
A sound source moves at a constant velocity. A listener is standing at a distance L away from it. Given that the source moves in a straight line at a right angle to the listener and starts closest to the listener (ie at t=0) deduce an expression for the frequency heard by the...
Homework Statement
I read that when a body approaches a stationary one which emits radar waves, the wavelength λ2 of the returned waves is longer than λ1, the wavelength of the emitted ones, but I get the opposite. I suppose this is true for sound waves also.
See picture.
The Attempt at a...
Homework Statement
You are traveling north of wayne rd at 20.0m/s, when you notice an ambulance in the distance approaching you at a high rate of speed. Using an iPhone app, you measure the siren's frequency to be 1.427 kHz. From previous experience you know that the ambulance siren emits a...
Homework Statement
The security alarm on a parked car goes off and produces a frequency of 958 Hz. The speed of sound is 343 m/s. As you drive toward this parked car, pass it, and drive away, you observe the frequency to change by 95 Hz. At what speed are you driving?
Homework...
I have just read about the principle of Doppler effect.
However there is a point which seemed a bit tricky.
According to the book, when the source of wave is moving the apparent frequency to a stationary observer is given by the equation:
f'=true frequency*speed of wave/(speed of wave +...
When we analyze the light coming from a distant galaxy, we find a particular absorption line with a wavelength of 1118 nm. This same absorption line in light from the sun has a wavelength of 625 nm is this galaxy moving towards us or away from us?
Calculate the magnitude of the velocity of...
Homework Statement
Hello, I'm working on an experiment that involves a Michelson interferometer and doppler effect.
Here is the description of the apparatus.
Michelson interferometer is set up with one moving arm and microwave is transmitted and received.
With the beam splitter splitting...
Homework Statement
A stationary observer at a crosswalk hears an ambulance siren with an apparent frequency of
480 Hz when the ambulance is approaching. After the ambulance passes the apparent frequency is only 420 Hz. Find the speed of the ambulance. Assume v = 343 m/s for the speed of sound...
Homework Statement
A doppler effect problem:
A sodium atom is emitting radiation at a wavelength of 6000 angstroms. When measured however the wavelength is widened to 6000 +/- 0.02 angstams. If this is primarily due to the doppler effect, what is the temperature of the sodium atom...
Hi All,
I would like to know how can one explain the assimmetry in Doppler effect. I will illustrate what I mean.
If a source emits 440 Hz but is coming in my direction with a velocity V (measured in m/s) I will hear, let's say, 441 Hz. Now, if the source is at rest with respect to the...
Homework Statement
In a distant galaxy, an emission line of hydrogen that has a rest wavelength of 656 nm has an observed wavelength of 662.6 nm. Is the galaxy moving away from us or toward us? How fast is it moving in (km/sec)?
Homework Equations
velocity = ((shifted wavelength -...
Homework Statement
A source S and a detector D are initially at a distance of x=1km. Both start moving towards one another with same acceleration a = 10m/s2. Frequency of source is f = 2000Hz. Find the frequency observed by the detector at time t=4s. Speed of sound in air is v=300m/s
The...
Hi.
I am learning special Relativity and I am seeing that the answer to the twin paradox involves the Doppler effect, and I am struggling to understand what is going on.
First let me explain what I know about the Doppler effect.
If an object produces waves (might it be light waves or sound...
I'm doing a night course in General Relativity and we're currently finishing off Special Relativity... We're working mainly off of D'Inverno.
We've just covered the relativistic doppler effect and some associated things like aberration.
When it came to talking about the transverse doppler...
Imagine this scenario:
An aeroplane emits a sound wave. The sound wave propagates in all directions.
a) If the plane is flying forward, it emits a sound towards a reflector in front of it. When the sound is reflected, its frequency is reduced, presuming the plane is traveling towards the...
At page http://www.qsl.net/vk3jed/doppler.html" is discussed Doppler shift at various ham radio frequencies. I calculated for this Doppler shift relative velocity of their satellite as 6720 m/s. Their satellite in height of 800 km above ground and at circular orbit should have velocity of 7453...
Homework Statement
A source and detector are placed a certain angle \phi apart on the edge of a rotating disk. The source emits radiation in all directions at a frequency \omega_* in its instantaneous rest frame. What frequency is the radiation detected at? (Hint: Little information is...
Hi, I'm interested in the derivation of the gravitational redshift formula from the Doppler shift in an accelerated frame formula (or viceversa), that are linked by the Equivalence principle, it should be pretty straightforward but I get stuck. Anyone can show me this or point me to a link with...
When we first realized that the further away a galaxy is the further towards the red side of the spectrum it was, we beleived this to be do to the expansion of the universe? Wouldn't it have been simplier to say that the further away a galaxy was the further the wave function stretched over...
Homework Statement
A bat, flying at a constant speed of 19.5 m/s in a straight line toward a vertical cave wall, makes a single clicking noise and hears the echo 0.15 s later. Assuming that she continued flying at her original speed, how close was she to the wall when she received the echo...
Did u ever try to explain Doppler effect for light in depth, at the photon level ?
I'm no scientist.
I'm trying to find a visual or mental representation of the doppler effect for electromagnetic waves.
There is no medium to vibrate. No way I can understand the phenomenon by making a...
I've been trying to graph an idea I had, but frankly I don't understand SR well enough to ensure my assumptions are correct, and that I'm using the correct formulas. I would appreciate any input/corrections you folks could give. Here's the idea, which I'll follow with my assumptions:
Idea...
Homework Statement
A car is getting closer to a radar as a speed of 135 km/h. If the radar works at a 2 \times 10 ^{9} Hz, what difference of frequency is observed for the radar?Homework Equations
\mu=\frac{\mu _0 \sqrt {1- \frac{v^2}{c^2}}}{1-\frac{v}{c}}The Attempt at a Solution
I converted...
I know that photons hitting a solar sail can add energy to that sail.
I know that photons are gauge bosons.
I know that gauge bosons are thought to be the carriers of fundamental forces.
If a solar sail were gaining speed to a point where it reached relativistically with respect to the power...
Problem:
Three radio-equipped plumbing vans are broadcasting on the same frequency,f0. Van 1 is moving north of van 2 with speed v, van 2 is fixed, and van 3 is moving west of van 2 with speed v. what change in frequency (f-f0) does van 3 hear from van 2? From van 1?
Attempt at solution...
Homework Statement
Firstly, whilst reading all this more complicated (and far more interesting) physics in other threads I feel like a dunce posting something which is probably of 'lower' level here as it were, but here goes:
If we have a vehicle like a police car (with siren going) moving at...
We observe farther galaxies with higher redshifts.
How can we be sure that this is due space itself expanding?
How do we know that this is not just Doppler shift of galaxies running away from us at higher speeds long time ago, that got lowered (decelerated by gravity of matter in the...
I have always been taught, that we can tell how fast a galaxy is moving away from us by it's amount of doppler shift.
If the atoms in the stars of those galaxies are moving very fast (i.e. that galaxy is moving faster than our galaxy is moving), relativity would have a bigger effect on them...
Homework Statement
An automobile is approaching you at a speed of 60.0 km/h and sounding its horn. The fundamental frequency of the horn sounds to you like 388 Hz. If the real fundamental frequency of the horn is 369 Hz, what is the speed of sound?
Homework Equations
Doppler...
Homework Statement
An ambulance is traveling at 84.0 km/h. The ambulance has a siren which produces sound at a frequency of 1.7 kHz. Assume the speed of sound in air is 345.0 m/s.
A police car is traveling at a constant speed of 80.0 km/h directly towards the ambulance. The police car...
Homework Statement
An ambulance is traveling at 72.0 km/h towards an intersection. Jim stops his car to give way to the ambulance as shown in the diagram below. In the diagram, the angle θ = 41.0 °.
The ambulance has a siren which produces sound at a frequency of 2.1 kHz. Assume the speed...
Homework Statement
A car is traveling at 30m/s in still air. the frequency of the siren on the car is 600hz. The velocity of sound in still air is 330 m/s. what is the wavelength of the sound waves
a)directly in front of the car
b)directly behind the car
What is the frequency of the...
Homework Statement
A French and a U.S. submarine are moving directly towards each other during manoeuvres in still water. The French submarine is moving at 50.0 km.hr-1. It sends out a sonar signal at 1100.0 Hz. The frequency detected by the French submarine (reflected back from the U.S...
Homework Statement
A French and a U.S. submarine are moving directly towards each other during manoeuvres in still water. The French submarine is moving at 50.0 km.hr-1. It sends out a sonar signal at 1100.0 Hz. The frequency detected by the French submarine (reflected back from the U.S...
Homework Statement
A stuntwoman is preparing to take a punch, crash through a "candy glass" window, and fall a long distance. The script calls for her to emit a piercing scream just before she hits the "ground." In reality, she will land on a waiting airbag. Lights! Camera! Action! The...
If as a result of the equivalence principle we can derive the gravitational red shift entirely from the perspective of an accelerating body with no reference to gravity and no reference to gravitational time dilation then one is essentially just working out the Doppler shift of a signal...