Doppler Definition and 749 Threads

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...

A train (source) approaching a stationery observer, wavelength of the sound is equal to the distance between source and observer, How?

How do scientists know if something is traveling away from us at any given moment, yes, it might be red, but it could be just a red dwarf star? How do they know it is the Doppler Effect in action, not just its natural colour?

Homework Statement The precision in measurements of radial velocities by the Doppler effect is currently 1 m/s. Can a Jupiter like planet orbiting a star similar to the Sun at a distance from the mother star equal to the Sun-Jupiter distance be detected?' (Use www or other sources to find the...

Hi, I'm a medical student who is using ultrasound to measure cardiac strain. I'm trying to read up a bit on the physics behind doppler imaging (I did AP physics in high school), and I have a question for some genius out there. I keep reading that in pulsed wave doppler measurements, one does...

Hello all, so I've always wondered about the expansion of the universe as indicated by the observed doppler (red) shift... i get the observed spectrum change and how this can be credited to the stretching of electromagnetic waves... what doesn't make sense to me is that if this is due to a...

Hi, I was hoping that somebody might be able to help me better understand/verify a Doppler model from the perspective of both a stationary and moving reference frame. For the current purpose, this Doppler model might be generally described in terms of sound waves in air, where air is assumed to...

Homework Statement the observer is stationary , but the sound source is moving towards the observer , i was told that the speed of sound relative to the observer doesn't change. why is it so ? in my opinion, the speed of sound relative to observer changed . because of v= f x (lambda) , as...

Homework Statement Trying to find the formula to generate a sin wave that would compensate for the Doppler effect if played from a car moving 50 mph past a stationary observer 1 meter from the car's path.Homework Equations ƒ_{observed} = \frac{v}{v+v_{s}}ƒ_{source}The Attempt at a Solution...

1. Homework Statement You are standing on side of road and ambulance drives by. Smallest distance between you and ambulance is 4m. Ambulance v=10m/s^2. You have 2.2 GHz radar. Ambulance travels 100m with center of straight line directly across from you. Compute exact doppler shift by taking...

Homework Statement The Sun rotates with a period of 24.7 days and has a radius of 7.00 x 108 m. For a terrestrial observer, Calculate the resultant Doppler shift of light of wavelength 500 nm which is emitted from the solar equator at : i)each side of the disc, ii)the center of the solar disc...

I have come to learn that the Doppler shift equation is asymmetric. That is, the Doppler shift is not the same when source is moving towards the observer or when the observer is moving towards the observer (both with same speed). I have looked at the derivation of the Doppler shift equation...

Homework Statement can anyone explain why reletive velocity is (v-u), based on my understanding, as the obesrvers moving away, the distance of the f th wavefront and first waavefront increases. so i would say it's v+u . correct me if I'm wrong. thanks. Homework Equations The...

Homework Statement Find the frequency heard as you walk away from a building that has a fire alarm going off with a frequency of 2650 Hz. The velocity of the alarm is equivalent to the final velocity of an object being launched with an initial velocity of 235.4 km/h [W23°N] from a height of...

I'm looking for an intuitive explanation for the redshift and blueshift phenonema that occurs when a light ray is emitted transversely. According to wikipedia: Assuming the objects are not accelerated, light emitted when the objects are closest together will be received some time later...

If a star races toward Earth the emitted light will be blue shifted. If the violet light produced from the star has a wavelength of 400 nm and it is blue shifted to 1 mn, does this light now exist as x-rays (on earth)?

Homework Statement In Minkowski spacetime, two observers, A and B, are moving at uniform speeds u and v, respectively, along different trajectories, each parallel to the y-axis of some inertial frame S. Observer A emits a photon with frequency nu_A that travels in the x-direction in S and is...

I was watching a video on the doppler effect by edx.org. The video said that the second wave of light given out, when the star(the light emitting object in this case) moves towards you, is not as big as the first one. So, it does not extend beyond the original wave. Why does this happen?

To calculate the detected frequency from the source frequency, we use this formula: { f }_{ D }=\frac { v\pm { v }_{ D } }{ v\pm { v }_{ s } } { f }_{ s } where {v}_{s}, {v}_{D} are velocities of the source and the detector respectively with reference to the medium. My question is why do...

Homework Statement Space probes communicate with controllers on Earth using radio waves. Suppose a probe has a radio-transmitter that operates at a frequency of 516.0 MHz when at rest relative to the observer. This probe is now wandering the solar system. The signal you pick up from the probe...

This is not homework but rather a concept question. If there was a siren on the front of an airplane that is traveling greater than the speed of sound, would there still be a sound emitted? If the airplane was traveling toward me what would be the frequency? Would I heart it? Where...

Hello, For convenience, we can say that a submarine at some depth in sea emits sound wave which refracts from the surface of the sea and is caught by a helicopter at some height above the sea. If we know the speeds of the submarine and the helicopter and the frequency of the emitted wave...

Hi all! Let me use an example to make this clear. There is a car traveling directly toward a man at 10m/s. The car is pressing down its horn, producing a frequency of 100hz. The speed of sound is 330 m/s. What frequency does the man hear? Ok, so we can use the equation: f_observer=(...

I understand mathematically etc how light can doppler shift when looked at as a wave but can it be understood how light doppler shifts as a photon i.e. could just one photon be doppler shifted? For example; Say there is an atom with energy levels 1 and 2. One observer, stationary relative to...

I've just begun to study spectroscopy, and I need a clarification about the Doppler Effect. Consider a cell containing Rubidium and enlight it with a laser. Connect the system with an oscilloscope and give a triangular wave as input (so you can know when the Rubidium is resonant). This is the...

Homework Statement There is a classic story (likely apocryphal) about an astronomer who was caught by a policeman for running a red light. The astronomer went to court and pleaded innocent, saying that the motion of his car made the red light (with a wavelength around 700 nm) shift to a green...

Hello! I'm was wondering if there is anyone that could help a Marine Biologist finding a "simple" way to calculate the sound amplitude degradation with the increasing distance. For example a source produces a sound of 237 dB re 1μPa at 1m (x) and the speed of sound in the water is 1500m/s (y)...

I have read that, the light from a distant moving object is tested for doppler shift to calculate its velocity. My question is, we can only lay our hands on the modified frequency, not the original frequency. So how to calculate the doppler shift from that?

In http://arxiv.org/abs/0808.1081 / Am.J.Phys.77:688-694,2009 Bunn and Hogg explain how cosmological redshift can be interpreted as accumulation of infinitesimal Doppler shifts. This suggested to invert z = z(v) and interpret v(z) as relative velocity of two objects with redshift z. It seems...

Hi, I have problem understanding some things about this particular LDV system(a Laser Dopler velocimeter). Source is a light source - laser. On the right there is a flow seeded with particles that scatters the light. So here we have a simple directional 3DB coupler. Light goes...

Could you please clarify for me how much each of these contribute to the red shifting of light from distant objects? It seems to me that red shifting of light from near by objects i.e. within our galaxy would be affected more by the Doppler effect whereas for intergalactic objects the red...

Homework Statement Homework Equations Shown below The Attempt at a Solution I know I probably did something wrong...but what?

Homework Statement A parachutist leaps from a hovering helicopter, after 4.0s of freefall shouts back at 425Hz. What frequeny is heard at the helicopter? Homework Equations f'=f/(1+Vs/V)Vsource=? f'=? f=425Hz V=343m/s The Attempt at a SolutionI'm stuck on finding the speed for the jumper...

Homework Statement A fire truck emitting a 450 Hz signal passes by a stationary detector. The difference in frequency measured by the detector is 58 Hz. If the speed of sound is 345 m/s, how fast is the fire truck moving? Homework Equations frequency of observer = (velocity of sound...

Hello everyone, Here is something I've discussed with some colleagues recently and that generated a lot of disagreement, so I wanted to bring the topic to Physics Forums to ask what is your understanding of the situations and wheter you agree with the "solution" I provide below or not. Imagine...

Homework Statement A laser emits a monchromic beam of wavelength λ, which is reflected normally from a plane mirror, receding at a speed v. What is the beat frequency between the incident and reflected light? Homework Equations The Attempt at a Solution The solutions starts off...

If light from a moving away object, such as a star, would appear red-shifted (and blue in case of approaching object), why don't we conclude that the speed of light is affected from that. Doesn't it mean that since light from a moving away object appear red, then the speed of light with respect...

Hey all, I was just wondering something which I couldn't get my head around tonight. If special relativity states that the speed of light is constant for all observers, regardless of the reference frame of any observer, then how is it possible for light to Doppler shift? Wouldn't the...

How do Doppler shifts work for light if, according to special relativity, light is constant velocity for all observers? So if c is unchanged, then surely wavelength and frequency don't change. I appreciate that I must be misunderstanding something, because redshift on stars occurs, but I am...

Homework Statement Two trains are traveling toward each other at 30.0 m/s relative to the ground. One train is blowing a whistle at 480 Hz. (a)What frequency is heard on the other train if the wind is blowing at 30.0 m/s toward the whistle and away from the listener? (assume the speed of sound...

Hey all, new to the forum. Had a tough question that I was trying to work out about an orbiting pulsar and the doppler shifted pulse period. So, if we have a pulsar orbiting some central object in circular orbit, with a constant orbital velocity v, and a pulse period of P_0, how can we write...

Hello, the internet. I am attempting to graph Doppler Shift as a function of time for a music project. The equation for observed frequency is: fo=fs(c)/vs(c) Where fo is observed frequency fs is the source frequency c is the speed of sound vs is the velocity of the source But...

A and B leave from a common point and travel in opposite directions with relative speed v. When B’s clock shows that a time T has elapsed, he (B) sends out a light signal. When A receives the signal, what time does his (A’s) clock show? Answer this question by doing the calculation entirely...

Consider a spaceship and a source, with no relative motion but spatially separated. At t=0, spaceship moves with velocity v \hat{a}_x w.r.t source and at t = 0 source emits a photon. After photon has been emitted, the speed of spaceship starts increasing in same direction. So what parameters...

Hi, I was looking up the formula for this on wikipedia and it said that the frequency shift is: \frac{\sqrt{1 - v^2/c^2}}{1+\frac{v}{c}\cos{\theta}} In the case where the the emitter is directly above the observer when the photon arrives it says it simplifies to: \gamma =...

I've got a somewhat simple question, and I think its from me overlooking something stupid...but how does using doppler shift work if in any moving rest frame the speed of light is supposed to stay at 3(10^8) m/s? I know that E=hc/λ, so for the wavelength of the light λ to change, the only thing...

Hello, I have to conduct a literature review in regards to Laser Doppler Anemometry and Impinging Air Jet. I am doing a project and it is to compare real velocity data obtained from LDA to CFD data and was wondering if anyone had any good books they could recommend for me to read or good...

Homework Statement A fly is moving with a speed vl=3m/s and a bat is chasing it with vs=5m/s. The bat is emitting a sound with fs=50kHz. They are moving on the same line towards point C which is a source emitting a sound at f'=57Hz. Find the frequency of the total sound the fly is hearing. The...

Hello, I was hoping someone might be able to help explain what the following are, I have found many articles but non which explain it in Lehman's terms: Probe Volume Bragg Cells Also can someone explain how the effect of varying beam angle is not under our control, but it can tell us...

Homework Statement What's the doppler shift (Δf) of the object moving away from us if we measure a wavelength of light λ=1.55μm emitted from it and it's at a distance of 10 megaparsecs? And is the object red or blue shifted? Added information to the problem is for each megaparsec the object...