Doppler Effect Calculator
Calculate the observed frequency change due to relative motion between source and observer
Calculate Doppler Effect
Original frequency of the wave source
Speed of wave in medium (default: 343.2 m/s for sound in air)
Positive if moving toward source, negative if moving away
Positive if moving away from observer, negative if moving toward
Doppler Effect Results
Formula used: f = f₀ × (v + vᵣ) / (v + vₛ)
Input values: f₀ = 0.00 Hz, v = 343.20 m/s, vᵣ = 0.00 m/s, vₛ = 0.00 m/s
Velocity Sign Convention
Receiver Velocity (vᵣ):
- • Positive (+): Moving toward source
- • Negative (-): Moving away from source
Source Velocity (vₛ):
- • Positive (+): Moving away from observer
- • Negative (-): Moving toward observer
Example: Ambulance Siren
Scenario
Situation: You're riding a bicycle at 15 km/h, ambulance approaches at 60 km/h
Siren frequency: 700 Hz
Sound speed: 343.2 m/s (air at 20°C)
Before Passing
vᵣ = -15 km/h = -4.17 m/s (away from source)
vₛ = -60 km/h = -16.67 m/s (toward observer)
f = 700 × (343.2 - 4.17) / (343.2 - 16.67)
f ≈ 727 Hz (higher pitch)
After Passing
vᵣ = +15 km/h = +4.17 m/s (toward source)
vₛ = +60 km/h = +16.67 m/s (away from observer)
f = 700 × (343.2 + 4.17) / (343.2 + 16.67)
f ≈ 676 Hz (lower pitch)
Result
Frequency change: 727 - 676 = 51 Hz difference in perceived pitch
Types of Doppler Shift
Blue Shift
Frequency increases
Source and observer approaching
Red Shift
Frequency decreases
Source and observer separating
No Shift
Frequency unchanged
No relative motion
Real-World Applications
Emergency vehicle sirens
Medical ultrasound imaging
Police radar speed detection
Astronomical observations
Weather radar systems
Blood flow measurement
Physics Tips
Higher frequency = higher pitch (blue shift)
Lower frequency = lower pitch (red shift)
Effect is proportional to relative velocity
Wave velocity depends on medium properties
Understanding the Doppler Effect
What is the Doppler Effect?
The Doppler effect is the change in frequency or wavelength of a wave for an observer moving relative to the source of the waves. It was first described by Austrian physicist Christian Doppler in 1842.
Physical Principle
- •When source and observer approach, waves are compressed (higher frequency)
- •When source and observer separate, waves are stretched (lower frequency)
- •Effect depends on relative velocities and wave speed in medium
Doppler Formula
f = f₀ × (v + vᵣ) / (v + vₛ)
- f: Observed frequency (Hz)
- f₀: Emitted frequency (Hz)
- v: Wave velocity in medium (m/s)
- vᵣ: Receiver velocity (m/s)
- vₛ: Source velocity (m/s)
Sign Convention: Positive velocities indicate motion toward each other, negative velocities indicate motion away from each other.
Applications in Different Fields
Medicine
Ultrasound imaging uses Doppler effect to measure blood flow velocity and detect heart conditions by analyzing frequency shifts of reflected sound waves.
Astronomy
Red shift and blue shift of light from stars and galaxies help determine their motion relative to Earth and provide evidence for universe expansion.
Technology
Radar systems measure object velocities, weather patterns, and aircraft speeds by analyzing Doppler shifts in reflected radio waves.