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Waves
Waves

Doppler Effect (Approaching)

f′=fv+vov−vsf' = f\frac{v + v_o}{v - v_s}

Frequency increases when source and observer approach.

Variables

f'
Observed frequency
Higher frequency
Hz
f
Source frequency
Emitted frequency
Hz
v
Wave speed
Speed in medium
m/s
v_o
Observer velocity
Toward source
m/s
v_s
Source velocity
Toward observer
m/s

Derivation

Special case of general Doppler formula.

Your notes

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Common questions

What is the Doppler Effect (Approaching) formula?

Doppler Effect (Approaching) is written f' = fv + vₒ/v - vₛ. Frequency increases when source and observer approach. It belongs to Waves, under Doppler Effect.

What are the units in f' = fv + vₒ/v - vₛ?

In SI units, f' is observed frequency, measured in 1/s; f is source frequency, measured in 1/s; v is wave speed, measured in m/s; v_o is observer velocity, measured in m/s; v_s is source velocity, measured in m/s.

How is the Doppler Effect (Approaching) formula derived?

Special case of general Doppler formula. The result is f' = fv + vₒ/v - vₛ.