What is the Doppler Effect?
A
Change in loudness of sound with distance
B
Change in frequency or wavelength due to relative motion of source and observer
C
Reflection of sound waves from a surface
D
Superposition of two sound waves
Analysis & Theory
The Doppler Effect is the change in frequency (or wavelength) of a wave when there is relative motion between source and observer.
When the source moves towards a stationary observer, how is the sound frequency perceived?
Analysis & Theory
As the source approaches, wavefronts get compressed and the observer hears a higher frequency.
When the source moves away from a stationary observer, the sound heard has:
Analysis & Theory
As the source recedes, wavefronts spread out, lowering the observed frequency.
Which of the following applications uses the Doppler Effect?
A
Measuring wind speed using radar
D
Measuring temperature with a thermometer
Analysis & Theory
Doppler radar is widely used to measure wind speed and weather patterns using frequency shifts.
If a car blowing its horn moves rapidly towards you, what happens to the pitch of the sound you hear?
Analysis & Theory
When approaching, frequency increases, so pitch appears higher.
Which of the following waves can exhibit the Doppler Effect?
C
Both sound and electromagnetic waves
Analysis & Theory
Doppler Effect applies to all types of waves, including sound, light, and electromagnetic waves.
What happens to the observed wavelength when the observer moves towards a stationary sound source?
C
Wavelength remains unchanged
D
Wavelength becomes zero
Analysis & Theory
When the observer moves towards the source, the apparent wavelength decreases, increasing frequency.
Which formula represents the observed frequency when the source is moving towards a stationary observer?
Analysis & Theory
When source moves towards observer: f' = f (v / (v - vs)), where v = sound speed, vs = source speed.
Astronomers use the Doppler Effect to:
A
Measure distance of stars directly
B
Determine motion of stars and galaxies (red shift and blue shift)
D
Calculate surface temperature of stars
Analysis & Theory
The red shift and blue shift due to Doppler Effect help determine whether celestial bodies are moving away or towards us.
When the source and observer move in the same direction with equal speed, the Doppler Effect is:
Analysis & Theory
If both move with the same velocity in the same direction, their relative velocity is zero, so no Doppler shift is observed.