Knott's equations

In geophysics, Knott's equations were the first equations to describe the amplitudes of reflected and refracted waves generated at non-normal incidence upon an interface.

[1] They were derived in 1899 by the British geophysicist Cargill Gilston Knott using displacement potential functions[2] and describe the same phenomenon that the Zoeppritz equations describe in terms of amplitude displacements.