Longitudinal frequency shift from speed

Doppler effect is also applicable to electromagnetic waves in vacuum. As there is no any medium required for these waves to propagate, speed of source related to observer is used for the calculation of the Doppler effect.

Notes:

  1. This is a special case, when wave speed in medium (vacuum) is close to speed of light. But relativistic version of classical Doppler effect is more general case, that includes non-electromagnetic waves.

Conditions:

  1. Source and observer are moving directly towards or away from each other.

  2. Wave speed is close to speed of light. It means this law is only applicable to electromagnetic waves.

  3. Motion is in 1D space.

Links:

  1. Wikipedia.

observer_frequency

Observer temporal_frequency.

Symbol:

f_o

Latex:

\(f_\text{o}\)

Dimension:

angle/time

source_frequency

Source temporal_frequency.

Symbol:

f_s

Latex:

\(f_\text{s}\)

Dimension:

angle/time

relative_speed

Relative speed between source and observer.

Symbol:

v

Latex:

\(v\)

Dimension:

velocity

law

f_o = f_s * sqrt((c - v) / (c + v))

Latex:
\[f_\text{o} = f_\text{s} \sqrt{\frac{c - v}{c + v}}\]