Free · Physics models
Classical Doppler Frequency Along a Line
Relate source and receiver frequencies for motion along the wave path in a stationary medium.
- Formula & worked example
- Private in your browser
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Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
A 1,000 Hz source, 340 m/s wave, receiver approaching at 10 m/s and source approaching at 20 m/s give 1,093.75 Hz.
f = f0 (v + vr)/(v + vs).
Worked example
Enter these known values and leave the other values blank.
- Emitted frequency (f==0==)
- 1000 Hz
- Wave velocity (v)
- 340 m/s
- Receiver velocity toward source
- 10 m/s
- Source velocity away from receiver
- -20 m/s
- Observed frequency (f)
- 1093.75 Hz
Assumptions and limitations
- Velocity signs follow the displayed formula: positive receiver velocity is toward the source, while positive source velocity is away from the receiver.
- This is the nonrelativistic, one-dimensional classical wave model in a stationary medium. It does not implement the relativistic light Doppler effect or oblique motion.
- Use positive wave speed and frequencies, and source and receiver speed magnitudes below wave speed. Sonic and supersonic cases are outside this branch.
- Enter known quantities and leave the unknown blank. Editable quantities support inverse solutions and locks; inconsistent locked quantities are reported. Unit selectors convert the quantity independently of its display.
- Reviewed hash-pinned model correction: Velocity signs follow the displayed formula: positive receiver velocity is toward the source, while positive source velocity is away from the receiver. This is the nonrelativistic, one-dimensional classical wave model in a stationary medium. It does not implement the relativistic light Doppler effect or oblique motion. Use positive wave speed and frequencies, and source and receiver speed magnitudes below wave speed. Sonic and supersonic cases are outside this branch. Enter known quantities and leave the unknown blank. Editable quantities support inverse solutions and locks; inconsistent locked quantities are reported. Unit selectors convert the quantity independently of its display.
Common questions
How do I enter an approaching source?
Use a negative source velocity. Positive source velocity is away from the receiver under this sign convention.
Does this apply to light?
The calculator uses the classical stationary-medium relation. Relativistic light shifts require a different equation.
How do I use the inverse calculation?
Clear the quantity you want to find and enter the remaining known values in their selected units. The model can only solve branches with enough independent information.
References
Enforce the documented finite physical branch and inverse domains.