Visible Light- What the Human Eye Sees

Wave length and colour

Electromagnetic radiation comes in different wavelengths which ranges from radio waves to gamma rays. Electromagnetic radiation is made up of both particles and waves. They can be looked as, changing electric and magnetic fields which propagate through space, forming an electromagnetic wave. The electromagnetic spectrum is the distribution of electromagnetic radiation according to energy or according to the frequency of wavelength.

Visible Light

Visible light (or Light) is simply a name for a range of electromagnetic radiation with in the spectrum that can be detected by the human eye and is responsible for the sense of sight. The human eye is very sensitive towards this radiation, and the various frequencies that our eyes interpret as colours. The window of human visible light is only a tiny fraction of the spectrum, roughly 400nm to 700nm.

The Electromagnetic Spectrum

In the human visible 400nm to 700nm range, 400nm corresponds to violet, and 700nm to the colour red. There is actually a continuous change from violet, blue, green, yellow, orange to red, as the wavelength increases. You can see this in the diagram above. Frequencies below 400nm or above 700nm are not able to be seen by the average human eye. Average because everybody is different.

Black is a total absence of light.

Luminaires emit light at a particular wavelength that is specified by a number represented in nanometers (nm).

White light is a mixture of the colours of the visible spectrum.

Yellow Light– The visible yellow light has a wavelength of about 570 nm.

Full Spectrum Lighting 

Full-spectrum light is light that covers the electromagnetic spectrum from infrared through near-ultraviolet, or all wavelengths. “Full-spectrum” is not a technical term when applied to an electrical light bulb but rather a marketing term implying that the product emulates natural light. Colour temperature (Kelvin) and Colour Rendering Index (Ra) are the standards for measuring light.


Rachel McCann

Photovoltaic Lighting Group


At PLG we specialise in being able to custom design standalone solar lighting system for our customers’ requirements. PLG   luminaires are made with the latest reflective technology and uses American Bridgelux high- power LEDs. LED’s are the fourth generation in Lighting and produce a natural white light for optimal night time lighting.





Categories: Lighting Technology

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