Visible Light

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What is Visible Light?

Visible light represented on the electromagnetic spectrum

Visible Light is the natural agent that stimulates sight and makes things visible. Light is electromagnetic radiation within a certain portion (band) of the electromagnetic spectrum. Light usually refers to visible light, which is visible to the human eye and is responsible for the sense of sight. The band of electromagnetic radiation that constitutes visible light has wavelengths (λ) ranging between 400–700 nanometres (nm) (or 4.00 × 10−7 to 7.00 × 10−7 m).


Why is Visible Light important?

Besides sensory stimulation being an obvious reason for light’s importance in everyday life, recording light intensity, or the energy delivered by visible light, lends understanding to the effects it may have on other readings and how low intensity or high intensity light conditions may impact other readings.

The relationship between the intensity of visible light and that of ultraviolet radiation is highly relevant when assessing exposure levels for weather reports. This is particularly relevant in the case of additional factors such as cloud cover (and by extension cloud density) and seasons that may alter the relationship.


How is Visible Light measured?

SL01 ☒CHIP

Light is measured with two main alternative sets of units: Radiometry consists of measurements of light power at all wavelengths, while Photometry measures light with wavelengths weighted with respect to a standardised model of human brightness perception, or in other words, measures light taking into account how the human eye responds to light. Photometry is useful, for example, to quantify illumination (lighting) intended for human use.

In the case of ☒CHIPS, visible light is measured in photometric units.

It is important to distinguish between luminous flux, which is luminous (light) energy over time (SI unit: lumen - lm) and illuminance, which is luminous flux per unit area (SI unit: lux - lm/m2). Luminous flux typically measures light from a particular source (e.g. the power of a flashlight) while illuminance is a better measure of the ambient light of an environment (e.g. how brightly lit a room is).

The light sensor on the SL01 ☒CHIP measures illuminance in lux.