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...
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...
[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...
First, let me clarify if my understanding of length contraction is correct. Is it accurate to say that relativistic velocities not only affect the measured length of an object in the direction of motion, but also the distance to the object from an observer in the direction of motion? For...
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
A kid is riding a bike and is ringing bell of 3000 Hz. You are standing still on the sidewalk.When the bicycle moves toward you, you hear a shift in the frequency of the bell. In addition, when the bicycle moves away from you, you hear a different shift in the frequency of the bell. If there is...
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...
< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color]
Last week we had to conduct an experiment with the aim of determining the speed of sound. I decided to play with doppler effect.
I was more or less sure what I had to do but then the...
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...
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 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...
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...
Homework Statement
[FONT=Arial]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...
Homework Statement
[FONT=Arial]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...
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...
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
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...
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...
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)...
Homework Statement
Taking light collected by the telescope and shine it through a diffraction grating with a 765.5 lines/mm. Using the filter that just the brightest Helium II line. you cast the diffraction grating's diffracted pattern on a screen is 22.000cm away and there are 3 dots, m=-1...
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!
Homework Statement
A speaker emitting sound at a frequency of 20 Hz is moving in the +x direction between two detectors. The speaker is moving at a speed of 30 m/s and the detectors are wired so that they flash red (λ = 700 nm) when the pressure is a maximum and green (λ = 700 nm) when the...
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,
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'...
Hello,
I am in search of some movie suggestions that incorporate different concepts such as sound waves, magnetic fields, doppler effect, transmission of light, inverse square law. The movie doesn't need to necessarily incorporate all of those concepts. I am working on a school project and need...
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...