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• What is light
• The laser principle
• Light and material
• Economic aspects
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What is light, how is it transported and shaped?

Light
Light is almost ubiquitous in our lives, and is usually experienced as something self-explanatory. In fact all of our life is oriented towards light. But where does this mysterious light come from, which can bring us light from the moon, for example, within a few seconds at a speed of approximately 300,000 kilometres per second?

Origin
Light arises directly out of atomic and molecular processes. A simple picture is offered by the Bohr atomic model, in which electrons are seen as orbiting around the atomic nucleus like the planets around the sun. When energy is introduced, electrons are lifted on to a higher orbital. In the transition from the higher orbital to a lower one, energy is released and emitted in the form of a photon. As the distance between the individual orbitals always has a certain value, the wavelength of the light emitted is always the same. There is therefore a single, very particular colour.

Wavelength, spectrum Natural light has various different wavelengths (corresponding to different colours) and only a small part of the colour spectrum is visible for us. Short wave light is violet and becomes part of the ultraviolet range, while long wave light goes from still visible dark red to the infrared range which is no longer visible for us. Light sources Apart from the sun, there is a range of other light sources such as for example an incandescent light bulb. Such light sources have a broad colour spectrum and radiate in all directions. The effectiveness of a light bulb as its visible light component is relatively small at approximately 5%. By far the most light is emitted in the form of infrared radiation, which we experience as warmth.