In the context of a plane wave, the terms "amplitude" and "frequency" refer to different aspects of the wave.
The amplitude of a plane wave represents the strength or magnitude of the wave. In the case of an electromagnetic wave, such as light, the amplitude refers to the maximum strength of the electric and magnetic fields associated with the wave. In practical terms, the amplitude can be related to the brightness or intensity of the wave.
The frequency of a plane wave, on the other hand, refers to the number of complete oscillations or cycles of the wave that occur in a given time. It is typically measured in hertz (Hz) and represents the rate at which the wave oscillates.
In the context of a laser, a laser beam can be described as a plane wave. The amplitude of the laser beam corresponds to the strength of the electric and magnetic fields, which determines the intensity of the laser light. The frequency of the laser beam represents the number of oscillations of the electric and magnetic fields per unit time, which corresponds to the color or wavelength of the laser light.
So, while both amplitude and frequency are used to describe a plane wave like a laser beam, they refer to different properties of the wave: amplitude describes the strength or intensity, while frequency describes the rate of oscillation or the color/wavelength.