Ultraviolet Light from the Sun


Transparency Master

 When sunlight is passed through a prism it is broken up into its component wavelengths forming the colour spectrum of visible light.

When a thermometer is placed slightly outside each end of the spectrum the temperature rises dramatically, indicating that there are "invisible" rays of energy being absorbed by the thermometer!

The invisible rays at the very bottom of the spectrum, below the red, are called infrared radiation using the word infra - the Latin word for "below". The invisible rays at the top of the spectrum, beyond the violet, are called ultraviolet radiation using the word ultra- from the Latin word for "beyond".


Transparency Master

 In the optical part of the Sun's spectrum, the infrared light has the lowest energy.

Infrared radiation cannot be seen, but it can be "felt". When we put our hands close to a hot object, without actually touching it, the sense of warmth that we feel is caused by our hand absorbing the infrared radiation emitted by the hot object.

The energy (of each photon) of light radiation increases as we move from red to violet. Ultraviolet photons of light have the highest energy of radiation in the optical spectrum and therefore cause the most cell damage when they are absorbed by skin cells.

Ultraviolet light can not only cause severe sunburn, but it also has the potential to cause skin cancer. At the very least, over-exposure to solar uv (ultraviolet) causes premature aging of the skin.

Plants, like humans, also suffer damage from exposure to ultraviolet radiation. Some plants are able to develop a protective cellular coating if they are gradually exposed to solar ultraviolet radiation. Other plants experience stunted growth, deformed leaves, and sometimes death.

Luckily, the Earth's atmosphere helps absorb most of the Sun's most dangerous ultraviolet radiation.

[Home]