Doppler effect Definition and 486 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 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...

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...

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...

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...

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=(...

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...

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...

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...

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...

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...

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...

Homework Statement A state trooper chases a speeder along a straight stretch of road; both vehicles move at 160 km/h. The siren on the trooper's vehicle produces sound at a frequency of 500 Hz. What is the Doppler shift in the frequency heard by the speeder? Homework Equations...

Homework Statement http://grephysics.net/ans/8677/12 I don't understand how it increases it's frequency by a factor of 10, I mean the total velocity goes from 1 to 1.9, therefore It seems like it should increase from 1kHz to 1.9kHz. Why is my 'common sense' wrong?

hi i just want to ask about the formula of Doppler Effect . The speeds of the listener VL and the source Vs are relative to the ground, source, or listener ?

I am currently capturing and analyzing spectra. My analysis software includes allowances for Doppler shifts resulting from relative radial motion between source and observer, and also Earth’s rotation. Results are accurate . The basic introduction to the Doppler effect generally starts with...

Homework Statement The source of a 1 kilohertz sound is getting closer to the listener at a speed of .9 times the speed of sound. What frequency does the listener hear? Homework Equations fl = ((v-vs) / (v + vl))fs The Attempt at a Solution ((343+343(.9)) / 343)*1000=1900 Hz...

Homework Statement An ambulance is moving in an expressway at a speed of 60km/hr from East to West(from A to B) as shown in the figure with a siren of 880Hz. Let the frequecies of the siren sound detected by an observer located at point O be Va and Vb as the ambulance just passes point A and...

I am a high school teacher and I just came across this issue when I began teaching at a new school. I am positive that if I am stationary and a 500 Hz siren comes towards me at 30 m/s, then the observed frequency will increase. I am 99% positive that if the 500 Hz siren is stationary and I move...

I have done a little analysis of Doppler Effect and have tried to compile my thought in a document. My background is not physics thus, I am seeking validation/criticism from this community. I would very much appreciate it if you went through my work and pointed out where I might be wrong. The...

Doppler Shift/ Doppler effect! HELP 1. A police car is traveling at a constant speed of 110. km/h with a radar gun which generates and detects radiowaves. The police car and the ambulance drive directly towards each other. The radar gun produces radiowaves with a wavelength of 0.0440 m. An...

Hi! I was doing some exercises about the doppler effect on sound until I found this problem that I can't find the solution! "A source of sound of frequency f0 moves horizontally at constant speed u in the x direction at a distance h above the ground. An observer is situated on the ground at...

Hello, We proved something during the course but I totally forgot how to do it.. Homework Statement Prove that Planck's Law E=h*u is deduced from the equation of Doppler effect u'=u*√((1-β)/(1+β)) Homework Equations Lorentz transformationThe Attempt at a Solution If we take a beam of light of...

Homework Statement A student is at some point between two sound reflecting walls. He's holding a tuning fork and runs towards one of the walls at 5m/s. The pulsating frequency he hears is 8Hz. ¿What's the sound frequency emitted by the tuning fork? Answer: 137.17 Hz. I know I'm supposed to use...

Homework Statement A listener L hears the siren from a moving police car ,S, which is moving away from the listener with a speed of v = 20.0 m/s. The listener is moving at 10.0 m/s towards the car. There is a wind blowing with a speed of v(wind)= 10.0 m/s from S to L. The siren is emitting...

Homework Statement A hooter on a motorcycle sounds a note of 6000Hz when the motorcycle is stationary. You detect a shift in frequency of 30Hz when the motorcycle approaches you and then recedes from you. Calculate the speed of the motorcycle. Speed of sound = 340m/s Homework Equations...

Homework Statement So you're being pushed on a swing by someone who is whistling at a constant 60Hz. At the bottom, Vmax is 4 m/s. Explain what you hear as you swing toward and away from the source of whistling (speed of sound is 343 m/s for this problem). Homework Equations Observed...

I pay for chegg to help me with physics but sometimes I'm not quite sure if the site is right. Could you please tell me if I am doing the below problem correctly? My way is different than Chegg's so I would just like to make sure I am not wrong because I am getting different answer than that...

Homework Statement A lighthouse emits a noise with a frequency of 2000 Hz in the direction of the sea, with a power of 100W. Consider the speed of sound, vs, to be 341 m/s. A ship approaches the coast with a speed of 30 km/h and produces noise with an intensity of 40dB. Consider it is...

Can any of you help. I am trying to fight a speeding ticket with a written declaration. To be honest I feel it was so unfair I was going with the speed of traffic and marked me as going 6mph more. I am sending the court explaining how I believe this was wrong and a radar error. Taking Physics...

Homework Statement taken directly from Rindler A large disc rotates at uniform angular velocity ω in inertial frame S. Two observers O1 and O2 ride on the disc at radial distances r1 and r2. They carry clocks C1 and C2 they adjust to keep with clocks time with S, i.e., they have been adjusted...