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Waves
Waves

Doppler Shift (Light)

Δλλ=vc\frac{\Delta\lambda}{\lambda} = \frac{v}{c}

Approximate Doppler shift for electromagnetic waves when v << c.

Variables

Δλ
Wavelength shift
Change in wavelength
m
λ
Rest wavelength
Original wavelength
m
v
Relative velocity
Source-observer velocity
m/s
c
Speed of light
≈ 3×10⁸ m/s
m/s

Derivation

Non-relativistic approximation of relativistic Doppler formula. Positive v = receding (redshift).

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Common questions

What is the Doppler Shift (Light) formula?

Doppler Shift (Light) is written Δλ/λ= v/c. Approximate Doppler shift for electromagnetic waves when v << c. It belongs to Waves, under Doppler Effect.

What are the units in Δλ/λ= v/c?

In SI units, Δλ is wavelength shift, measured in m; λ is rest wavelength, measured in m; v is relative velocity, measured in m/s; c is speed of light, measured in m/s.

How is the Doppler Shift (Light) formula derived?

Non-relativistic approximation of relativistic Doppler formula. Positive v = receding (redshift). The result is Δλ/λ= v/c.