- In any particular situation, the relative amplitude of an electromagnetic wave correlates with the relative intensity of light falling on a surface and the relative brightness of the colour perceived by an observer.
- As the amplitude of an electromagnetic wave increases so does the overall distance between the peak and a corresponding trough.
- The greater the amplitude of a wave, the more energy it carries.
- The energy carried by an electromagnetic wave is proportional to the amplitude squared.
- The amplitude of the electric field of an electromagnetic wave is measured in volts per metre and the magnetic field in amperes per metre.
About amplitude, brightness, colour brightness and intensity
The terms amplitude, intensity and colour brightness are sometimes confused.
Amplitude is a feature of electromagnetic waves. Other features include:
Intensity measures the energy carried by a light wave or stream of photons:
- When light is modelled as a wave, intensity is directly related to amplitude.
- When light is modelled as a particle, intensity is directly related to the number of photons present at any given point in time.
- The intensity of light falls exponentially as the distance from a point light source increases.
- Light intensity at any given distance from a light source is directly related to its power per unit area (when the area is measured on a plane perpendicular to the direction of propagation of light).
- The power of a light source describes the rate at which light energy is emitted and is measured in watts.
- The intensity of light is measured in watts per square meter (W/m2).
- Cameras use a light meter to measure the light intensity within an environment or reflected off a surface.