The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
A common example of Doppler shift is the change of pitch heard when a vehicle sounding a horn approaches and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.The reason for the Doppler effect is that when the source of the waves is moving towards the observer, each successive wave crest is emitted from a position closer to the observer than the crest of the previous wave. Therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrivals of successive wave crests at the observer is reduced, causing an increase in the frequency. While they are traveling, the distance between successive wave fronts is reduced, so the waves "bunch together". Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wave fronts is then increased, so the waves "spread out".
For waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source are relative to the medium in which the waves are transmitted. The total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium. Each of these effects is analyzed separately. For waves which do not require a medium, such as electromagnetic waves or gravitational waves, only the relative difference in velocity between the observer and the source needs to be considered, giving rise to the relativistic Doppler effect.
If I am stationary and a sound source moves towards me at a constant velocity, I will hear it (the sound) increase in frequency until it is adjacent to me and then as it moves away from me, I will hear a decreasing frequency.
Fundamental stuff right? It works with radio waves and light which is...
Homework Statement
The light from galaxy NGC 221 consists of a recognizable spectrum of wavelengths. However, all are shifted to the shorter wavelength end of the spectrum. In Particular, the calcium "line" ordinarily observed at 396.85nm is observed at 396.58nm. (a) is this galaxy moving...
To my understanding the Relativistic Doppler shift is a product of the classical velocity shift and the dilation factor arising from that velocity.
The classical effect can be red or blue depending on whether the emitter and receiver are receding or closing respectively.
The dilation...
I'm trying to understand Doppler and specifically I'm trying to get the same answer as I look at the same situation in different frames. I'm getting stuck though and getting a slightly different answer in one frame, hopefully someone can help me understand.
Here's my simple example. There...
Could "Redshift" not result from the Doppler effect?
Redshift is the astronomical phenomenon where galaxies and other far-away objects appear shifted to the "red" side of the visible light spectrum. The farther an object is from us, the more pronounced this shift is. This phenomenon is most...
A police car is traveling at a constant speed of 100. 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 0.0650 m.
What doppler shift (Δf = f′–f) is detected...
Hello,
This one has been bugging me for a while. When you drive a car past parked cars that are somewhat close, with the window down, there is a rhythmic whooshing sound. This sounds very much like numerous dopplershifts, but I have difficulty seeing it as a doppler shift because the parked...
Homework Statement
A car and a bicycle are traveling directly toward each other at different speeds. The car horn has a frequency of 440Hz, and the car is traveling at 15.0m/s. The cyclist hears a sound of frequency 467Hz. The velocity of sound in air is 343m/s.
i) Calculate the frequency of...
I recently heard about the effects from The Doppler Effects at high relative speeds (significant fractions of c).
For example you will eventually will even get burned/die by the radiation of the CMBR being ao intensly blueshifted while you're approaching the speed of light (relative).
So...
If the doppler effect is the changing if wavelengths due to movement of a light source (In reference to light of course), does this mean the distance between the wavefront and the source changes at a speed DIFFERENT from C? doesn't this mean that if the observer is in the plane of the source the...
Hi all. I am asking for some help with getting a physical intuition for the following situation:
Consider an observer and source, at rest. The source emits sound waves of a particular frequency, 'f'. Letting the medium (air for example) between the source and the observer move with a particular...
Homework Statement
In the figure, a motionless observer stands between sound sources A and B, which oscillate at 338 Hz and 342 Hz, respectively. The observer hears a beat. Next, when the observer begins moving at a constant speed on the straight line connecting A and B, the beat is no longer...
Given the Doppler shift equation quoted here: http://en.wikipedia.org/wiki/Doppler_effect#General
\frac{f_r}{f_s} = \left(\frac{c + v_r}{c + v_s} \right)
where
c is the velocity of waves in the medium;
vr is the velocity of the receiver relative to the medium;
positive if the receiver is...
I tried to wiki this,which stated relativistic doppler effect takes time dilution into account,but the analogy/example given was not related to time dilution..can anyone summarise both with a practical situation or a useful link for it
Thanks in advance
Homework Statement
I'm working on this problem here:
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/redshf2.html
The answer is already listed, it's the steps I'm worried about.
I don't see how they get from step 1 to step 2 here. They don't even tell me what T is. It seems...
doppler formula help please!:)
Hello, i see the doppler formula in 2 different forms one being f1=f2 (Vw/Vw-Vs) and the other f1=f2/(1+Vs/Vw)
f1= Doppler frequency
f2= Source frequency
Vw= Speed of sound
Vs= Speed of source
the problem i am having is understanding how these are...
I was considering the following question;
'A fire engine traveling at 70m/s drives past a van traveling at 30m/s. The speed of sound in air is 330m/s and the fire engine has a frequency of 200Hz when stationary. At what frequency does the van driver hear the siren?'
I understand you have...
If this is the wrong place to be posting this, feel free to lock this thread. I wasn't sure if this belonged in "classical physics" or "quantum physics"; this seemed like the appropriate place, but I'm not 100% certain, as it does involve subatomic particles.
Anyways, to get to the matter at...
Homework Statement
Radar is used to measure the speed of passing vehicles. A stationary radar gun emits EM radiation, a proportion of which is reflected from the target vehicle which is moving away from the gun at 'u' ms^-1.
a)State the frequency at the target vehicle (f.tar) in terms of...
Consider a stationary observer and an emitter of light radiation that may be either receding or approaching at a variety of nonrelativistic velocities, with the velocity of the emitter having only a radial component and no transverse component.
I was wondering whether the Doppler Effect...
Homework Statement
a) Calculate the Doppler shift due to a relative velocity of 3cm/sec.
b) Fine \Delta E/E, where E = 14.4keV and \Delta E is the Doppler shift obtained in (a).
Homework Equations
\frac{f_{0}}{f_{s}}=\frac{c}{c+v_{s}}
The Attempt at a Solution
So I'm working on...
Ive been going through some landers of Venus and Mars and I found they were equipped with radio doppler experiment(http://en.wikipedia.org/wiki/Venera_9 )
I was wondering what this does.
I mean there is radio signal transmitted through space everywhere and i suppose the device would measure...
I love to do mathematics, but apply it to usually classical physics, and no doubt quantum mechanics (since it's mainly just maths), and most other things except some astronomy. I don't mind calculating the orbits and so on, but I don't like calculating doppler shifts and etc. Does anyone else...
The relationship linking the emitted frequency Fe and the received frequency Fr is the Doppler Law:
F_r = \sqrt \frac{1-\frac{v}{c}}{1-\frac{v}{c}} F_e
The Taylor series for the function \sqrt\frac{1+x}{1-x} near x = 0 is 1+x+\frac{x^2}{2}+\frac{x^3}{3}+...
On Earth, most objects travel...
A source and a receiver is at rest with each other. Source emits some couple of light pulses, and stops emitting more.
1. The pulses is not reached to the receiver yet, and source starts moving. Does the receiver experience doppler effect with the emitted pulses?
2. The pulses is not...
Assume a object in motion emits a beam of light at an observer.
The observer detects a frequency that is higher than the original frequency.
That is the measured energy of the photon by this observer is higher than it was while emitting.
How to account for this extra energy?
thanks,
kalpak
Homework Statement
How to find the radar resolution? Homework Equations
Doppler frequency = 2v/wavelength
f = 2B
R = ct/2
The Attempt at a Solution
I don't know how to take the length of the aircraft into consideration.
I only know how to calculate the doppler frequency but not the range...
In my physics books it gives an equation of frequency for a moving observer as
f'= v'/λ =v+u/λ. Since λ=v/f it was converted to f'=v+u/(v/f) = (v+u/v)f
I understand this much of the equation, but the final Algebraic factoring that I don't get is they said this equation is f'=...
Homework Statement
You are cruising to Jupiter at the posted speed limit of 0.1c when suddenly a daredevil passes you, going in the same direction, at 0.3c. At what wavelength does your rocket cruiser's light detecter "see" his red tail lights? Is this wavelength ultraviolet, visible, or...
To find out how fast you would have to be going in order to to see a green light when the light is infact red what doppler equation would you use. I used f = ((c+v)/c)*f0. Is this wrong, if so why?
From the special relativity theory , for explaining the red-shifting of a photon, that has been red-shifted, is the following:
point O: origin point of emitted photo, in Galaxy GlxO
point R: receiving point of photon, in Galaxy GlxR
GlxO, O ---------->----------------R, GlxR
Suppose...
I have re-written this as as I accidently deleted my original post. I was wondering if the relativistic Doppler shift of a reflection from a mirror moving away from the observer was the same as the Newtonian equation in the special case that the mirror is orthogonal to the direction of motion...
Homework Statement
A detector initially moves at a constant velocity directly toward a stationary sound source and then (after passing it) directly from it. The emitted frequency is f. During the approach the detected frequency is f'app and during the recession it is f'rec. If the...
I solved for parts and a and b of this problem and need someone to check the answers for me and help me with part c.
A) 467.5 Hz
B) 5.45 m/s
Jane is standing on the platform waiting for the train. The train approaching the platform from the north at 20 m/s blows its whistle when it is 100 m...
Homework Statement
The observer sees first spaceship that is moving from the right towards him with the speed v_r=0.6c, and the second ship that is coming from the left with the speed v_l=0.8c.
If the first ship emits a signal with the frequency of 10^4 Hz (measured in the reference frame...
Homework Statement
There is a question asking the frequency of a distant location from two rotating speakers which are attached to the both ends of a meter ruler. The ruler is rotating ar 7 rounds per second and A speaker has a frequency of 500Hz. At the given time they are in a position which...
does doppler effect affect ENERGY of photon??
i have tried to make the question as clear as possible,but in the process,have made it a bit too long. i request you to be patient-
suppose a source is emitting a photon after equal intervals of time.an observer,who was initially at rest w.r.t the...
When I ask for differences I am not meaning mathematical ones since that it is obvious:
We have a phenomenon p, p can be described by Galilean Relativity (GR)
and by Einsten Relativity (ER).
ER(p)!=GR(p)
The math expression that describes this phenomenon is different.
Then the doppler...
Homework Statement
A woman is riding a bicycle at 18.0 m/s along a straight road that runs parallel to and right next to some railroad tracks. She hears the whistle of a train that is behind. The frequency emitted by the train is 840 Hz, but the frequency the woman hears is 778 Hz. Take the...
Homework Statement
A policeman detects a drop of 10% in the pitch of the horn of a motor car as it crosses him. If the velocity of sound is 330ms^-1, calculate the speed of the car.
Homework Equations
f2 = f1 [v - v(listener)]/[v - v(source)]
where f2 = apparent frequency
f1 =...
The image shows four points. "A" is source of light and "B" is receiver, and "a" and "b" represents co-ordinate points.
"A" is moving with constant speed to "B". "B" feels doppler effect.
If "B" moving with constant speed to "A", then also "B" feels doppler effect.
Statement 1: This two...
Homework Statement
A microphone is attached to a spring that is suspended from the ceiling. Directly below on the floor is a stationary 540-Hz source of sound. The microphone vibrates up and down in simple harmonic motion with a period of 2.20 s. The difference between the maximum and minimum...
Homework Statement
Two auto-mobiles are driving on the same road in opposite directions. The speed of the first auto-mobile is 90.0 km/h and that of the second is 60 km/h. The horns of both auto-mobiles emit tons of frequency 524 Hz. Calculate the frequency that the driver of each...
Lets say we have some particle A 1m above the ground.
Let it has velocity v.
Also let's consider gravitons like the reason/mechanism of the gravitation.
Let gravitons moves away from the Earth with velocity c.
Now let's consider the differences between two cases:
1 when particle A moves down...
When a source emitting a sound of a specific frequency moves towards the face of a cliff at a speed. The frequency of the sound that reaches the cliff is for sure not the same as the frequency emitted from the source due to doppler effect.
Will the frequency of the sound reflected by the cliff...
Homework Statement
P15. The police car with its 300 Hz siren is moving toward a warehouse at 30 m/s, intending to crash through the door. What frequency does the driver of the police car hear reflected from the warehouse? (5 marks)
Homework Equations
doppler shift for an approaching...