The formula

(frequency) = (speed of light) / (wavelength)

was implicitly combined, in 1905, with Axiom 1 (so Einstein's special relativity emerged), but it can also be combined with Axiom 2:

Axiom 1: The speed of light is constant.

Axiom 2: The wavelength of light is constant (for a given emitter).

Axiom 1 killed fundamental physics (converted it into an insane ideology). Axiom 2 will resurrect it (if it's not too late).

It is easy to show (see https://twitter.com/pentcho_valev) that the wavelength of light remains constant

(A) when the observer starts moving towards the emitter.

(B) when the emitter starts moving towards the observer.

(C) when light falls in a gravitational field.

Pentcho Valev