Doppler Effect Simulator
Classroom worksheet · Interactive simulation: https://lkforge.com/tools/physics/doppler-effect/
Name: Date:
Learning objectives
- Explain how relative motion shifts observed frequency.
- Predict the shift for approaching and receding sources.
- Connect the effect to everyday and astronomical examples.
Variables to change
- Source speed
- Direction of motion
- Observer position
Procedure
- Set the source moving toward the observer and note the observed frequency.
- Reverse the direction so the source recedes and compare.
- Increase the source speed and observe the size of the shift.
Observations
Record the observed frequency as the source approaches and recedes at different speeds.
Questions
- What happens to observed frequency as a source approaches?
- What happens as the source recedes?
- How does increasing the source speed affect the shift?
- Give an everyday example of the Doppler effect.
- How do astronomers use the Doppler effect?
Answer key (instructors)
- 1. It rises above the emitted frequency (waves are compressed).
- 2. It falls below the emitted frequency (waves are stretched).
- 3. A faster source produces a larger frequency shift.
- 4. The pitch drop of a passing siren or car horn as it goes by.
- 5. Redshift of a galaxy’s light shows it is receding, evidence for the expanding universe.
Relative motion between source and observer changes the observed frequency: approaching compresses waves (higher pitch/blueshift), receding stretches them (lower pitch/redshift). Faster motion means a bigger shift — heard in passing sirens and seen in galaxy redshifts.