This quantity is the x-ax
This quantity is the x-axis of the Fletcher-Munson curves and the eponymous Bode plot. Reginald Fessenden invented a method of creating new values of this quantity called heterodyning. For an LC circuit, a form of this quantity is proportional to one over the square root of the product of inductance and capacitance. For a pendulum, a form of it is proportional to the square root of little g divided by length. The energy of a photon equals the product of this quantity and the Planck constant, and an observer perceives a shift in this quantity in the Doppler effect. For 10 points, name this quantity that has an inverse relationship to wavelength, and is often measured in Hertz.
This quantity is the x-axis of the Fletcher-Munson curves and the eponymous Bode plot.