In the context of electromagnetic waves, including light, the amplitude refers to the maximum displacement or strength of the electric and magnetic fields comprising the wave. The amplitude determines the intensity or brightness of the light.
When the amplitude of an electromagnetic wave increases, it means that the electric and magnetic fields become stronger. In the case of light, this corresponds to an increase in the intensity or brightness of the light. This is because the intensity of light is directly proportional to the square of the amplitude of the electric field.
In simple terms, when the amplitude increases, more energy is carried by the wave, resulting in a brighter or more intense light. This increase in energy can be visualized as a greater number of photons (particles of light) being emitted or absorbed, which leads to a higher perceived brightness.