Ultraviolet radiation

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What is Ultraviolet radiation?

Simplified diagram detailing UV electromagnetic spectrum

Ultraviolet (UV) radiation is electromagnetic radiation with wavelengths (λ) ranging from from 10 nanometers (nm) to 400 nanometers (or 1.00 × 10-8 m to 4.00 × 10-7 m), which is shorter than those of Visible light. Therefore, UV radiation cannot be perceived by most humans as typical human eyes to not have receptors for UV.

Why is Ultraviolet radiation important?

Illustration of UV subtypes from the atmosphere to our skin

Ultraviolet radiation constitutes approximately 10% of the total radiation output of our sun. While UV cannot be seen by most humans, it can be perceived by many species of birds, insects and fish. UV radiation is particularly notable for the damaging influence it has on the skin of humans and many other animals, as well as plants. Additionally, several synthetic materials such as certain plastics are damaged by exposure to UV radiation. Other sources of include specialized ultraviolet lights such as black lights and tanning lamps as well as electric arcs (from arc welding equipment).

The ultraviolet radiation that reaches Earth’s surface is divided into 2 subtypes: Ultraviolet A (UVA) with wavelengths (λ) between 315 nm and 400 nm and Ultraviolet B (UVB) with wavelengths ranging from 315 nm to 280 nm. UVC, a third existing subtype, which wavelengths range from 100 nm to 280 nm, is completely absorbed by Earth’s atmosphere (specifically by the Ozone Layer) along with most of the UVB radiation.

Ultraviolet radiation is mostly relevant in the eyes of the general public because of its impact on human health (see ultraviolet index) as there are both benefits, when exposure to UV is managed well and severe risks and consequences as in the case of prolonged overexposure.

How is Ultraviolet radiation measured?


Ultraviolet radiation intensity is measured using radiometers; of which there are 3 main types: Narrow Band, Broad Band and Spectrophotometers.

  1. Narrow Band radiometers filter out a very narrow band of wavelengths of the UV spectrum from either the UVA or UVB division.
  2. Broad Band radiometers (also called “Total UV” radiometers) have a response to a much broader band of the UV electromagnetic spectrum, with some models completely or mostly cover all of the UVA and UVB ranges of wavelengths.
  3. Spectrophotometers measure the intensity of the radiation over a spectral range at a large number of discrete wavelengths and are often used in biochemistry laboratories.

The intensity of UV radiation is measured in milliwatts per square centimeter (mW/cm2) or millijoules per square centimeter (mJ/cm2), which is energy per unit area per second. The Ultraviolet sensor on the SL01 ☒CHIP is a broad band optimized radiometer and measures both UVA and UVB.