Technically there is no such thing as a continuous wave, as any signal of finite duration (time) must be composed of multiple frequencies, and all signals are o

Technically there is no such thing as a continuous wave, as any signal of finite duration (time) must be composed of multiple frequencies, and all signals are of finite duration. This is closely related to the uncertainty principle in physics, whereby quantities that are related by a Fourier transform are also related by an uncertainty principle. Duration (time) and bandwidth (frequency) are related by a Fourier transform.