Colour
Within the visible light range of the Range of all possible frequencies of radiation, eg ultraviolet light is part of the EM spectrum., there is a A series of similar waves arranged in order of wavelength or frequency. of colour. This is a Variation that shows a wide range of intermediate values between two extremes. They can be measured. range of colours. In order of increasing The number of waves produced each second. The unit of frequency is hertz (Hz). (and decreasing The length of a single wave, measured from one wave peak to the next, or one wave trough to the next. ) these are given as:
- red
- orange
- yellow
- green
- blue
- indigo
- violet
Each colour within the visible light spectrum has its own narrow band of wavelength and frequency.
Reflection and absorption of colour
Waves can be Energy is 'taken-in' by the material and the internal energy of the material will increase, eg infrared radiation from the Sun is absorbed by the surface of the Earth. at the boundary between two different materials. When waves are absorbed by a surface, the energy of the wave is transferred to the particles in the surface. This will usually increase the The total kinetic energy and potential energy of the particles in an object. of the particles.
When white light shines on an Not transparent or see-through. object, some wavelengths or colours of light are absorbed. These wavelengths are not detected by our eyes. The other wavelengths are reflected, and these are detected by our eyes. White light is a combination of all of the colours in the visible light spectrum.
For example, grass appears green in white light:
- red, orange, yellow, blue, indigo and violet are absorbed by the grass
- green light is reflected by the grass and detected by our eyes
Coloured objects in coloured light
An object appears to be black if it absorbs all the wavelengths of visible light. For example, an object that appears blue in white light will appear black in red light. This is because the red light contains no blue light for the object to reflect.