8.3   WHEN THE SOURCE MOVES

It is interesting to calculate the parameters length and frequency of a beam of photons when its source moves with velocity u.

When the source moves the beam of light has velocity ç:

 ç = c + u

The De Broglie formula states that the light length is:

λ = h/mç

λ = h/(m(c + u)) = h/(mc(1 + u/c)) = λ₀/(1 + u/c)

then:

The light frequency is:

υ = ç/ λ = c(1 + u/c)/( λ₀/(1 + u/c)) = υ₀(1 + u/c)²