Light

Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. The three basic dimensions of light (i.e., all electromagnetic radiation) are:

Measurement of light

The following quantities and units are used to measure light.

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• brightness (or temperature)
• illuminance or illumination (SI unit: lux)
• luminous flux (SI unit: lumen)
• luminous intensity (SI unit: candela)

Light can also be characterised by:

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• brilliance (or amplitude),
• color (or frequency), and
• polarization (or angle of vibration).

SI light units