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What is Light?

Definition of Light

Light is electromagnetic radiation detectable by the human eye. Visible light occupies and is defined by a range of frequencies called the Visible Light Spectrum. The Visible Light Spectrum is usually expressed in terms of nanometers (nm) of wavelength rather than frequency in Hertz. In the lighting industry, the conventional range of the wavelengths for visible light is about 400 nm to 700 nm, as shown in the Visible Light Spectrum image.

Visible Light Spectrum

Lighting Terminology There is a unique vocabulary or terminology used to describe and measure various aspects of light. The Photometric Measurement of Light graphic lists some photometric terminology commonly used in the lighting business. For example, illuminance and luminance are common photometric terms that are similar but not the same.

Photometric Measurement of Light

 

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