Doppler Definition and 749 Threads

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?

Homework Statement Given the speed of sound in an environment, c = 300 m/s. We have an object moving with a ceratin velocity. If we know that the soundwaves behind the object are lower by 3 octaves than in front of it, then what is the velocity of the object? 2. Attempt at solving it. I...

I accept that what I write below will be unpopular and argued with vehemently, however I think it should be considered with an open mind and recognised for the sense that it has. Originally the concept of an expanding universe (and therefore by extrapolation the concept of the Big Bang that...

Dear PF Forum, I'd like to know how to measure speed only by doppler effect. What if we don't know the frequency? What if we don't know the distance? If we look this diagram on our computer screen, we'll know everything. Distance, speed, time dilation event relative simultaneity of event. But...

Dear PF Forum, I have a question again about Doppler effect in relativity. Before I ask about mirror and lamp, I want to refresh the discussion again as in my previous thread: https://www.physicsforums.com/threads/doppler-for-light.823942/ The formula for Doppler factor for light is. ##f =...

Dear PF Forum, I wonder about this Doppler formula. https://en.wikipedia.org/wiki/Doppler_effect#General ##f=(\frac{c+V_r}{c+V_s})f_0## The speed of sound is 343m/s Supposed S (Source) moves to the east, toward R(Receiver) at 70 m/s and R moves to the east at 40 m/s. So the formula is...

Good day to you all, I wanted to share a struggle with you all that I can't seem to get out of. It's about calculating, in the case of sound, the decrease or increase in frequency (thus increase or decrease in wavelength) when a sound source is respectively moving away or towards an observer...

Hi, Does Doppler effect differs in reason from sound to light ? I mean is the Doppler effect of sound just because changing velocity of sound? In the case of light it's because of merely time dilation

Homework Statement Emma and Don are playing in a band. While emma is marching toward Don, Don tunes his instrument to match the note that emma is playing. When emma stops, don immediately notices a beat frequency of 5 Hz. If the speed of the sound is 330m/s what is the relationship between...

Dear PF Forum, After so many questions about Twins Paradox and Universe Frame of Reference, I'd like to know about Lorentz and Doppler. First. Here V is ##\sqrt{0.75}## ≈ 86.60%. If we put V in Lorentz Transformation formula as speed, we'll have Gamma = 2. Okay here's the question. Two probes A...

Homework Statement A cyclist with a bell ringing with a frequency of 658.8 Hz drives towards a wall with a speed of 3.18 ms-1. Just before colliding with the wall the cyclist hears beats, due to the bell itself and the reflection of the sound from the wall. What is the frequency of beats...

Homework Statement A ball (like the one used in lectures) generating a sound with a frequency of 594 Hz is swung around in a large circle with a radius of 1.49 m. The time it takes the ball to travel around one complete circle is measured and found to be 0.96 s. the speed of sound in air is 343...

Homework Statement Find the observed frequency ##\nu## in terms of proper frequency ##\nu_0##, speed ##v## and radial velocity component ##v_r## for a source moving at velocity ##\vec v## with respect to the observer. Now consider an observer in frame S where the source is seen moving at...

Greetings , Many Doppler effect questions require to find the final Frequency/Wavelength. so after using the equation : Δλ / λ = v / c or Δf / f = v / c How can I know if the change in Frequency/Wavelength is positive or negative to calculate the final frequency or wavelength. because...

Hi, So i know that the doppler equation is as follos; F(observed)= (Vsound + Vdetector) / (Vsound +- Vsource) x F(emitted) Does anyone know how to reaarange the equation to solve for the other variables?

Homework Statement At an air show, a fighter jet does manuevers past the crowd. Your increible hearing notes that the frequnecy of the sound coming from the jet engine drops exactly by one octave when it is approaching you to when it is directly above you (not moving relitive to you). How fast...

Homework Statement I have to study laser cooling. I'm actually trying to understand the Doppler limit on temperature. On the net I have found "at a certain point the cooling mechanism is foiled by heating due to the random absorption and reemission of photons...

i need thee the derivation of relativistic doppler shift. i found its derivation in the book of Serway, but it is not in detail and step by step. in the book there is given that: can anyone give me the step after eq#1.13? how eq#1.13 converted in the form of eq#1.14?

Homework Statement A star travels in a direction transverse to the line of observation from Earth, with a speed 0.5c. It also emits light with wavelength ##\lambda_0## in the rest frame of the star. Calculate the wavelength of the light as observed on Earth, and also the angle at which the...

cosmological redshifts are caused by the metric expansion of space, whereas doppler shift is a result of relative velocities through space. So before the development of the modern cosmological models, how did astronomers originally distinguish these two causes of redshifts (e.g. when they tried...

Homework Statement A runner is running with speed V along the straight line connecting two identical speakers. Both speakers are playing a tone of the same frequency f. a)What is the beat frequency that the runner hears? b)If the standing wave forms between two speakers, how frequently will the...

Homework Statement You are moving at a speed of 35m/s and hear a siren coming from behind you and observe the frequency to be 1370 Hz. The siren goes past you and the new frequency heard is 1330 Hz. What is the speed of the siren traveling at? The speed of sound in air is 340m/s. f1=1370 Hz f2=...

Homework Statement As you drive at a speed of 15.0 m/s an ambulance approaches you from behind with its siren blaring at a frequency of 1022 Hz. After the ambulance has passed you the signal is now 981 Hz. If both you and the ambulance travel at a constant speed how fast was the ambulance...

Homework Statement As you drive at a speed of 15.0 m/s an ambulance approaches you from behind with its siren blaring at a frequency of 1022 Hz. After the ambulance has passed you the signal is now 981 Hz. If both you and the ambulance travel at a constant speed how fast was the ambulance...

Does anybody know a good read/primer that compares the observed cosmological redshift values to predictions made by the relativistic (gravitational) redshift? Thank you!

In contemplation and research regarding another thread's question about the asymmetry of doppler shift wrt the medium, I find myself trying to imagine two people talking... or perhaps better yet matching pitch. In still air with both people facing each other at ten paces of course they would...

Problem statement, work done, relative equations: I am unsure if I got this problem right, especially part (e) A star is moving at 0.2c along the x axis. The star is moving away from observer A and toward observer B. The star emits light with a maximum intensity at wavelength 500nm. (a)...

I noticed on my shadow that the left side had a blue outline, and the right side had a red out line, and it sparked my curiosity... It reminds me of the Doppler effect, because I came to notice that the side of the shadow that's furthest from me is always the red one, and the closer side is...

Homework Statement This isn't strictly a homework problem, but I didn't know where else to post this. I can't get the same derivation as my lecturer for the Doppler effect of light - which is shown in the attached file. If you cannot open this, I re-wrote it further down. Homework EquationsThe...

Ben is walking in a park in a straight line at 1.2 m/s. A bird is hiding in a bush. When Ben is closest to the bush, he is 2 m away from the bird and he hears a 10 dB sound. How long will he continue to hear the bird? Thanks for your help!

As we know, when the observer is moving away from the source, then the apparent frequency is, ##f_{observer} = f_{source} (\frac{v_{sound} - v_{observer}}{v_{sound}})## But, if ##v_{observer} > v_{sound}## , ##f_{observer}## becomes negative.

I am looking at derivations of the Doppler effect for sound and light, and I am very confused about what stays the same when it comes to sound. In this video, at 5:10, it is said that the wavelength will be the same. I'm not sure I agree with this because I'm pretty sure both the observed...

Hello to everyone! First I would like to go through one simple example: We have two bodies. One is wave source, other is wave receiver. In this example they are positioned like this: (source) O=====> (receiver) O=====> Distance between them is always 1000 m. Let's say that the waves are...

Is it possible to create a doppler shift of EM radiation in a lab? or is it only feasible on universal scales? I was just thinking that high energy x-rays have a sub-atomic wavelength,could these be transformed to visible light to let us 'see' an atom?

Hello, I've been thinking about what exactly is the doppler effect and I'm not sure I understand it because I thought it meant a change in frequency due to relative motion while at the same time its defined in terms of changing wavelength such as in red shift or blue shift. Case 1 The...

Hi everyone, I am having some problems understanding Bergmann's problems. Problem 3 from Chapter 4 from Intro to the Theory of Relativity by Bergmann 1. Suppose that the frequency at a light ray is f with respect to a frame of reference S. Its frequency f′ in another frame of reference, S'...

Homework Statement A train moving at a constant speed is passing a stationary observer on a platform. A flute player is playing a note with a frequency of 940Hz. after the flute has passed, the observer hears the sound frequency of 915Hz. What is the speed of the train? The speed of sound in...

Homework Statement Two trumpet players are both playing with a pitch of 440 Hz, corresponding to the musical pitch A above middle C. However, one of the trumpet players is marching away from you so that your hear a beat frequency of 4 Hz from the two trumpets. With what speed is the departing...

Homework Statement As you stand by a railroad track a train passes with its whistle blowing. As it passes, you hear a frequency shift equal to 21 % of the frequency of the whistle. How fast is the train moving. Express your answer in km/hr.(Speed of sound is 331.4 m/s) Homework Equations f’ = f...

The question "If light speed is constant, how do you explain the Doppler Effect?" has been asked a lot in the internet. Anyway, I haven't found one concise answer. In the book Kleppner&Kolenkow Mechanics there is a brief explanation of the Relativistic Doppler Effect, but as usual in this topic...

Hello, If been for a while trying to find information about how Doppler effect affects modulated signals. When a transmitter is moving relative to a receiver, the receiver will have a shift in the carrier frequency that will vary as the transmitter gets closer or moves away from the...

Hi, Consider a person who holds a light source of frequency f. Consider an observer who sees this light. The energy of each photon as received by the observer is E = hf. The observer is now fixed. Now suppose that the person who holds the light source starts to move towards the observer, then...

If an observer and a visible light source are in relative motion such that the visible light source is blueshifted to ultraviolet frequencies, then would this visible-light-turned-ultraviolet-light being received by the observer have the same properties as that of actual ultraviolet light i.e...

Homework Statement Problem: a car is moving away from a stationary observer at 25ms^-1. It emits a frequency of 810Hz and the observer hears an apparent frequency of 762Hz. What is the speed of sound in air at that time? Homework Equations The equation for a source moving away is f' =...

Hi, I'm trying to figure out exactly what colors a white light (i.e. the Sun) would look like to an observer traveling at varying relativistic velocities. Yes, moving away from it - red shift. Moving towards it - blue shift. In more detail, the human eye has a limited varying-amplitude...

Just some conceptual ideas that I don't understand A spaceship starts falling under gravity with an acceleration g as measured by an observer Barry at rest on Earth. At the instant that the ship starts to fall, an astronaut Harry at the base of the rocket ship sends a light signal of frequency...

Homework Statement Atomic hydrogen emits a characteristic spectral line with a frequency of 1421 MHz. A radio telescope observes this line in a certain galaxy at a frequency of 1432 MHz. Is the galaxy approaching or receding, and at what speed (in km/s)? Homework Equations The Attempt at...

A bat uses ultrasound at 40kHz to locate a stationary insect. If bat is flying directly towards the insect at speed of 4m/s at what frequency does the bat receive the ultrasound reflections from the insect? Speed of sound = 340m/s. I went frequency = frequency of source x (velocity of...