Doppler Definition and 713 Threads

Good day, I was playing a bit with a Doppler effect scenario and tried to combine it a bit with Special Relativity and I concluded something that I don’t quite understand, or that I at least don’t get the meaning of. I am aware that the scenario and my concluded formula don’t describe the full...

In his seminal paper on Special Relativity: On the Electrodynamics of Moving Bodies, Einstein derives a formula for the Relativistic Doppler effect. See this section: § 7. Theory of Doppler's Principle and of AberrationThe formula is: In this Wiki article, the same formula is derived. The...

I'm trying to render the sky as it would appear from a starship moving at some large part of the speed of light. Geometry was straightforward, but colors are the problem. How would the doppler effect change the color of a star? The expectation is that the stars behind are red and the ones ahead...

Homework Statement I'm watching this lecture and wanted to attempt to derive the expression for ΔTo/ΔTs Homework Equations ΔTo = ΔTs + VΔTo / U The Attempt at a Solution I have worked out that ΔTs = 1-V / U, however I'm stuck trying to get ΔTs / ΔTo because of the ΔTo on both sides of the...

[Note from mentor: this thread was originally posted in a non-homework forum, therefore it does not use the homework template.] I have been given an equation for the relativistic doppler effect but I'm struggling to see this as a function and then give a first order Taylor expansion. Any help...

Homework Statement http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_Paper3_2004_QP.pdf question 3. Should i post a picture of it if its more appropriate ? Note: I'm expected to do this in about an hour [Mentor note: Image of the relevant portion of Q3 inserted] Homework...

Let's say you have a sound emitter and receiver a fixed distance apart on a moving object but open to the air, such as on the hood of a car. The emitter is near where the windshield wipers are, and the receiver is closer to the grill. They are in aligned along middle of the car, longitudinally...

A very clever first-year physics student I know, who had just been learning about the Doppler effect, asked me a question. If a plane were flying a straight trajectory at Mach 2, playing a song on its speakers very loudly, and an observer with incredibly sensitive recording equipment were to...

I was wondering if it is possible to image the motion of individual air molecules? What I am picturing is using a laser to illuminate a volume of air, and using scattered light to measure the velocity of individual air molecules through the doppler shift of the scattered light. It seems that...

What happens if a source and the observer move at the same direction? Always hear how only one of them doesnot move, or when they move towards each other. For example. An ambulance moves towards direction A with Va. A biker moves towards direction A as well, with Vb. What happens to the...

I think the relativity provides the Doppler shift (in a radar - double version) in a form: ##\frac{1-v}{1+v}## which is quite simple, as a square of a single Doppler: ##f' = f\sqrt{\frac{1-v}{1+v}}## But I never seen what is a classical version of this - what is a formula for a radar shift in...

I would like to be sure about one case of the use of Doppler effect with sound waves. If the medium (in the case of sound air) is moving, but there is no relative motion between the observer and the source there is no Doppler effect at all. (And the absence of relative motion is...

Hi All, What is the explanation for the fact that doppler effect has an asymmetry with relation to the relative movement fo the source and the observer? For instance, ## \frac{v + 5}{v} \neq \frac{v}{v -5}## The version I have seems to be somewhat truncated to me; it simply relates this fact...

Homework Statement A source emits a spherical sound wave at frequency ##f=110Hz## with power ##P=1 W## in a solid angle of ##2 \pi sr##. An observer moves with velocity ##v_{oss}=108 km/h## towards the source. Determine the sound intensity level received by the moving observer. Homework...

How are the intensity of a sound wave and the Doppler shift of frequency related togheter? That is, if the source or the observer are in relative motion, how does the intensity change? For a sound wave $$I=\frac{1}{2} \rho \omega^2 A^2 c=2 \pi^2 \rho f^2 A^2c$$ (##c## is sound speed, ##\rho##...

Think at a cop car with a siren that moves with a velocity Vc, it emits a sound with a velocity C Now think about a person that doesn't move, in front of the cop car, shouldn't he register that the speed of the sound emited is Vs= Vc+ C? According to the galileian equations (true for v <<c...

When thinking of sound waves (or more commonly seen waves) the doppler effect is fairly obvious. A car is moving away from you, it's horn's membrane is fluctuating, increasing & reducing air pressure over time. So if it's moving away from you the sound's peak would occur further away...

Homework Statement Consider two parallel walls perfectly reflective placed at the distance ##d = 0.8 m ##. A ball, provided with a device through which are emitted continuously frequency sound waves equal to ##f_0=430 Hz##, is launched from one wall to another. It moves with constant velocity...

Hello, It kind of bothers me that the derivation for the Lorentz transformation relies on two dimensions of space. (Here I am referring to the standard derivation where one person is using a vertical light clock in a trolley traveling horizontally at speed v, and an observer outside is...

Homework Statement Hi, I'd really appreciate being pointed in the right direction with this past exam question, as I just have no idea how to approach it and can't find similar examples in my notes anywhere. A nearby star has a spectrum similar to the sun, suggesting it has the same mass. The...

Homework Statement A driver of a car traveling towards a wall with a speed of 5m/s, sounds a horn of frequency 256 Hz. If speed of sound= 330m/s, find a) No. of beats /sec if the observer is between the car and the wall. b) No. of beats/sec if the car is between the wall the observer. c)...

Say we have an observer in perfectly circular motion around a source, like a star. Is it reasonable to apply the angle change formula ##cos \theta_o = \frac{cos \theta_s - \frac{v}{c}}{1-\frac{v}{c}cos \theta_s}## and then take the component of the motion parallel to the light wave in the...

Homework Statement I have this Doppler effect formula, but I don't know how it was derived, I can't repeat the process myself to solve for speed of the source, I would really appreciate if someone could mathematicly solve this in steps, thank you very much. Homework Equations...

I'm looking at George Smoot's derivation on pp. 2-3 here: http://aether.lbl.gov/www/classes/p139/homework/five.pdf It's elegant and succinct, but I'm having trouble understanding the very last step. Using the Lorentz transformation, he gets this relationship: ##dt = dt^\prime \gamma (1 +...

I have been trying to find an per reviewed article where it is actually tested that sound does not have a transverse Doppler effect. I figure that its probably do to my lack of resources. if it is could somebody give me a link to the article i would appreciate it. If not, i must ask why has it...

Homework Statement A motor scooter moving at 10 m/s approaches and passes a police car moving at 50 m/s in the opposite direction. The frequency of the siren on the police car is 700 hz when the car stands still. the difference in frequency heard by the driver of the scooter between when the...

I'm looking for an EM wave solution to Maxwell's equations that matches the Doppler diagram below. That is, circular wavefronts that are not concentric due to the motion of the source. Does a solution that accurately matches the Doppler diagram exist?

full screen (high res) http://images.tinypic.pl/i/00765/8g7j8biccn4d.jpg Em Wave = LIGHT Em Wave = RadioEquator Source------L---------SensorHow big L we need use to register Doppler ? I wan to measure 360/24h speed Big Question ?! single arm we have Doppler (RED ) [ more long arm --->...

In ultrasound what is the difference between beam steering angle and Doppler angle thanks

Homework Statement When a train running at a speed of 72 km/h approaches a crossing signal, a passenger in the train hears the siren at 720 Hz. What frequency does the passenger detect after the train passes the crossing signal? Take the speed of sound in air to be 340 m/s. Homework Equations...

Imagine that there is a stationary source that is propagating waves (such as sound waves). Let's say that the wave speed in the medium is 343 m/s. If I am an observer, and I begin to move towards the waves, will the wave speed increase due to the idea of relative velocities, or will only the...

I was just looking at a few animations and something that could be just visualized incorrectly or I may have interpreted correctly is that the wavelengths coming from the sources are initially smaller close to the source, but become larger as you get far away from the source. Is there any...

How is E=mc^2 derived from relativistic doppler effect? I looked up on wikipedia but it seems to have some errors. https://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence#Alternative_version

I'm a bit confused about this. So say there's an observer and a source of sound. If the observer moves towards the source of sound, the frequency seems to increase because he encounters more wavelengths in the same amount of time. In a second case, if the source moved towards the observer, the...

If you had twin 1 on the earth, and twin 2 fly to a star and back at a speed of v with the Earth and star separated by a distance L, twin 1 sends out flashes at intervals of t seconds (measured in his frame). Taking into consideration the numbers of redshifted and blueshifted flashes that the...

Imagine a mother ship traveling away from Earth at .5c and a shuttle takes off from the mother ship in the same direction of travel at .5c relative to the mother ship. The shuttle fires a blue laser (400nm) to a transparent screen mounted on top of the mother ship as it is traveling away. Due...

I'm just trying to build Doppler shift equation for Moving observer and stationary source. I have an problem in a step. I'm attaching a screen-shot please check it and tell me where to this step ( 1 - v/u)^-1 comes from ? Thanks in advance.

Homework Statement At the initial moment source and detector are located in same point and are both in rest. Source is released into free fall and detector remains in rest. Source has frequency fs=512 Hz and speed of sound is v=340 m/s . When detector detects frquency f =485 Hz , what...

So the prof shows us how to tell if an object is red shifted, by comparing two spectra (i assume of the same object). The emission lines had similar gaps but were shifted right, therefore moving away from us. How can you obtain two different spectra of the same object if it's constantly moving...

Homework Statement Can't figure how to prove when both source and observer are moving that the observed frequency is the product of the two independent cases below.. Homework Equations We know individual cases when source is moving and observer is still, the observed frequency is equal to...

I have found a book from my father epoch of undergraduate student in Physics. It was apperently Physics 101, and was written with a typewriter and the formulae with pen. I have gone straight to Special Relativity section and, to my dismay, and even if all formulae were indeed correct, the...

[mentor's note - lightly edited to fix the Latex] Hi there, I was hoping if someone could clear my small misconception for this equation. f' = f \left( \frac{ 1- \beta }{ 1+\beta } \right)^2 I had thought if the numerator is negative and denominator is positive that means the signal of light...

Homework Statement Here is the problem: http://faculty.kfupm.edu.sa/PHYS/kuhaili/doppler_problem.htm {Mentor's edit: Here's the text copied from the url: A fire engine moving to the right at 40 m/s sounds its horn ( frequency 500 Hz ) at the two vehicles shown in the figure. The car is...

Hi all, I was just thinking about the Doppler effect today and I was wondering why distance between the source and listener does not affect the frequency experienced by the listener. Consider the Doppler formula: fL = fS*(v+vL)/(v+vS), with the positive direction taken from listener to source...

Hi. I understand the principle behind Pulsed doppler ultrasound. If the echo from a transmit pulse is sampled (gated) during a narrow fixed time period, the echo will correspond to a particular depth. What I do not understand is how we can extract phase information by repeating the process of...

Homework Statement In the picture below, can you help me understand what do equations 3 and 5 mean. They concern the soppler effect but i can't seem to understand what do they represent. Homework Equations ft + fv/c=ft((c+v)/c fd=ft-fr 3. The attempt at solution

Hello, I just thought of something that looks like a paradox to me. Suppose you have a device which can detect a light source's frequency, and will explode if the frequency exceeds a threshold value f_t. Place this device stationary wrt the light source. Now, suppose there are two observers, one...

Homework Statement I have been investigating the Doppler effect in a circular motion with a stationary source and moving observer (however the main aim is to determine the speed of sound in the end). Using Vernier software - Logger Pro - I have obtained two graphs of the sound pressure against...

I have a quick question about the Special Relativity. Non-relativistically, we expect no doppler shift in the wavelength of the emitted light if the source is moving at right angles to the line of sight to the observer. However there is a transverse doppler shift even in this case, caused by...

[Mentor's note - split off from https://www.physicsforums.com/threads/are-time-dilation-experiments-conclusive.826952/ as this is a different question] This makes sense. And fact they appear to slow down is due to red shift of light created between the two frames?