Doppler Definition and 749 Threads

Pretending the siren is at rest in air: Wavelength = velocity/frequence --> (343 m/s) / 10,000 Hz = .0343m. I don't believe this is the correct way to go about solving the problem, since the vehicle is moving at the start and the siren is not at rest.

If I and the light source are both moving toward one another, I see light blueshifted. What if I'm at rest and the source moving towards me?

I don't know what is wrong i think when bat gets sound f' = f×(c+v/c) when audience hears f''=f'×(c/c-v) f''=f×1.059 but it is wrong TT

Kindly don't delete the post again, I am a teacher. The question above mentioned came in Board Exams 2 years ago in our Country. We the group of teachers tried to solve but we found that the problems misses the required information to be solved. The data still seems to be the case of Doppler's...

Problem Statement: The Doppler effect is routinely used to measure the speed of winds in storm systems. As the manager of a weather monitoring sta- tion in the Midwest, you are using a Doppler radar system that has a frequency of 625 MHz to bounce a radar pulse off of the raindrops in a...

I found the beat frequency to be 4 Hz and the carrier frequency to be 260 Hz, but I'm not sure how to apply them to the solution/integrate the doppler and beat frequency equations?

Hi, absorption cross section in resonance depends on the relative speed of neutron and nucleus in Center of Mass frame. As you can see here https://www.nuclear-power.net/glossary/doppler-broadening/ Temperature plays a big role in determining resonance absorption cross. I don't understand why...

Homework Statement A Doppler flow meter is used to measure the speed of red blood cells. The frequency of the apparatus is f = 12 MHz. The sensor in the apparatus measure 1.8 kHz beats between the emitted frequency and the frequency of the ultrasound reflected back by the blood cells. The speed...

This is only something I’ve noticed, and in my eyes it’s odd, it may be utterly wrong or already well known but with some fancy term that I don’t know. Suppose an object- say, a clock- is moving towards you, at about .5c. For the moment, we will assume time dilation is negligible, and that you...

Homework Statement Imagine two planets orbiting a star with orbits edge-on to the Earth. The peak Doppler shift for each 70 m/s, but one has a period of 7 days and the other has a period of 700 days. The star has a mass of one solar mass. (Assume 1 solar mass equals 2E+30 kg.) Q1: Calculate...

I have seen people talking about measuring Doppler shift of stars to know how fast they are receding from us. But if I measured say a particular frequency f, how do I know whether this is shifted frequency or just the emission?

If you had an object moving away from you at near C and it was emitting light that was pulsed at 1 Hz (from the point of view of the object) and you were to view it from a stationary position (earth), what would you see? It would be red shifted and the pulse rate would be slowed down? Would the...

Homework Statement Derive the formula for the Doppler effect for a receiver traveling at an angle theta away from a planar source Homework EquationsThe Attempt at a Solution [/B] I thought that we can assume that the wavelength has two components ##λ_x## and ##λ_y## where ##λ_x = ct+vtcosθ##...

I have an obvious understanding failure here, so hopefully someone can help me clear this up. Thanks for reading this obnoxious drivel.Leading clocks lag So, if two clocks are fixed to a the ends of a barn, and they are set off with light pulses from the midpoint, in the frame of the barn the...

I have seen few examples on Doppler effect and i am confused about one such. We are standing on ground. If the source of sound S moves and Object O is stationary. We would presume the frequency as well as wavelength of sound be changed to the obeject O. But if O moves towards or away from S...

How does particle physics explain the doppler effect? (including blue/red shift)

When a force follows the inverse square law, its effects are stronger as the source approaches than when it recedes. So light will blue shift (higher energy) and sound is louder and at a higher pitch. So I would think that gravity would be stronger from an approaching object that from a...

In the video: The professor mentions how the wavelength will be the same for a moving observer vs a moving observer for a classical wave like a sound wave. However, how does that explain doppler shift? Don't we observe the effect because a moving observer measures a different wavelength than a...

Homework Statement Homework Equations [/B] delta lambda/lambda = velocity/speed of light radius of the sun= 696 *10^6mThe Attempt at a Solution Hello, the solution states the correct answer for this problem is 5.8*10^-12m. This is exactly 2x my answer but i don't really know what i did...

Hello all, (1st post) I would like some help with deciding if the source is moving towards the observer or vice versa in Doppler effect situations. The example that I am confused about is a skydiver holding a constant frequency emitting source during the descent. The skydiver is traveling at...

Homework Statement Two trains A and B have a whistle that blows at a frequency fT = 392 Hz. Train A is stationary and train B is moving toward the right (away from A) at a speed of vB = 35 m/s. A listener is between the two trains and is moving toward the right with a speed of vL = 15 m/s. No...

Homework Statement Homework Equations frequency of observer = frequency of source[(V +- Vo ) / (V-+Vs)] The Attempt at a Solution I am not completely understanding this question. I kinda understand that the frequency of the siren does not depend on the distance between the motorcycle and...

According to doppler shift you can measure low energy photons at one side of a star and higher energy photons at the other side of a star. How is this possible? I know the classical explanation but what happens on an atomic level?

Greg Bernhardt submitted a new PF Insights post Coordinate Dependent Statements in an Expanding Universe Continue reading the Original PF Insights Post.

It's already known in physical communities that the velocity of light always constant and not depend on motion of observer or source. But it is also teached to us that there are aslo Doppler shift experienced by light wave like that when measuring CMB radiation. But for me it is makes a...

Homework Statement Homework EquationsThe Attempt at a Solution When the source is not moving, ## \lambda = 6250 A ## ...(1) When the source is moving, ## \lambda ' = 6500 A ## ...(2) From (1) and (2), ## \lambda ' > \lambda ## ...(3) This means that the source is moving away from...

If we (a detector) are moving toward a star that emits a single photon (due to its distance) and that photon hits our detector, it will be blue shifted. My question is why. If the color of a photon is a reflection of its energy level and since the speed of the photon is always coming at us at...

Homework Statement A body emits photons of frequency ##\omega_*## at equal rates in all direction in its rest frame. An observer is moving with speed V relative to the body in the x direction. Find the rate at which the photons are received per unit solid angle ##dN/dt'd\Omega'## a large...

Homework Statement A sodium light source moves in a horizontal circle at a constant speed of 0.100c while emitting light at the proper wavelength of λ0=589 nm. Wavelength l is measured for that light by a detector fixed at the center of the circle. What is the wavelength shift λ-λ0? Homework...

Just a quick question I got in my mind while reading up about fission, the so called Doppler effect which manifests itself in fertile material like U238, I read it helps control reactor stability , hence the majority of fuel consists of U238, as the fuel heats up at some point, U238 starts to...

I just saw this news article on the home page of the university I'm working in: http://www.aalto.fi/en/current/news/2017-06-30/ It seems to be about a study that can potentially explain the redshift of distant stars with a mechanism that's related to the interaction of photons with the...

Homework Statement To determine the speed of a train, a student of Physics determined the frequency of the whistle in the approach to its position of observation, and measured 220 Hz. He then determined the frequency of the whistle when the train moved away, and got 190 Hz. What is the speed of...

I was driving the other day, and I was about to go past a green light when it turned yellow, so I sped up. I got past the light but but it got me wondering, how fast would you need to go for a red light to appear green due to the Doppler Effect. (Excuse me if this question doesn't belong in...

I would like to know the formula for calculating the Doppler shifted frequency received by someone on Earth that is received from a spaceship traveling at 85 percent the speed of light away from Earth. Please show example of the formula being used. Let's say the spacecraft sent a radio signal...

Hi, I was looking into Doppler shift calculations, and I came across this blog post. It gives a very simple and straight forward account of calculating the velocity of a star. Following is the summary the blog post: Spectrum of Alpha Centauri (A. Cen.) is obtained through Lhires III...

Hello! I am a bit confused by the Doppler effect. Based on the formula it seems that if the source moves towards me with speed ##v## I hear a frequency ##\nu_1## but if I move towards the source with the same speed ##v## I hear a different frequency ##\nu_2##. However according to the...

how does the doppler effect work when the observer and source are not moving in a straight line, what do we take in as the velocity of the observer and the source in the doppler effect equation?

Homework Statement A stationary police car emits a sound of frequency 1200 Hz that bounces off a car on the highway and returns with a frequency of 1250 Hz. The police car is right next to the highway, so the moving car is traveling directly toward or away from it. (a) How fast was the moving...

Homework Statement Why does a source moving perpendicular to the line between it and the observer produce no doppler effect?Homework Equations The Attempt at a Solution I have heard the the radial velocity of the source relative to the observer must be zero but i don't understand why, if the...

If a mode of light is in the single photon state in the reference frame of the emitter, what will the state look like in a reference frame where the wavelength is, say, 5% less or more? How about a state with, say, 5 photons? I saw some online discussions and some papers on arXiv (not...

robphy submitted a new PF Insights post Relativity Variables: Velocity, Doppler-Bondi k, and Rapidity Continue reading the Original PF Insights Post.

Consider at stationnary radar at the origin ##z=0## and a target (speed ##v##) moving along the ##z## axis and away from the radar. The radar is sending plane waves (frequency ##f_i##) to the target and they come back to the radar (the radar is then both an emitter and a receiver). I am...

Homework Statement A probe is launched with velocity v=0.8c. A beacon emits a light with wavelength \lambda=500nm in its rest frame. Years later the probe is located by NASA using a telescope, When they measure the light they find the wavelength \lambda=500nm in their rest frame. Is this...

Dear All, I have a couple of (noob) questions regarding Doppler Shift and light from a quantum physics perspective: a) Since different observers will see the light at different frequencies depending on their reference frame / velocity thus resulting in Doppler Shift, does that mean that any...

I have learned that the Doppler effect causes a change in wavelength (and thus frequency) in all types of waves Suppose there is a radio station transmitting waves of frequency 90 kHz and the antennae in my car is tuned to that frequency. Then I start to accelerate and thus I am changing my...

Homework Statement An avant-garde composer wants to use the Doppler effect in his new opera. As the soprano sings, he wants a large bat to fly toward her from the back of the stage. The bat will be outfitted with a microphone to pick up the singer's voice and a loudspeaker to rebroadcast the...

Homework Statement Show how one can obtain the Doppler transformation for the frequency of a receding source just using the Lorentz transformations for the energy (where E=h). Homework Equations Relativistic transformations for momentum and energy: E = γ(E' + vp'x) pc/E = v/c = β The Attempt...

Homework Statement A train moves at a constant speed of v = 25.0 m/s toward the intersection shown in Figure P13.71b. A car is stopped near the crossing, 30.0 m from the tracks. The train’s horn emits a frequency of 500 Hz when the train is 40.0 m from the intersection. (a) What is the...

Homework Statement A source emits sound with a frequency of 860 Hz. It is moving at 20.0 m/s toward a stationary reflecting wall. If the speed of sound is 343 m/s, what frequency does an observer riding with the source hear? A 860 Hz B 913 Hz C 910 Hz D 765 Hz...

Light consists of quanta(small packets of energy). Then how do we explain doppler effect of light the same way we do for sound? What is the valid explanation of light doppler effect which is consistent with the photon picture?