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a light source. Random (incoherent) light sources, such as stars and light bulbs, emit photons with random arrival times and a Bose-Einstein distribution. Laser (coherent) light sources, on the other hand, have a more uniform (but still random) distribution: Poisson.
Light sources Light sources can be divided according to different criteria: Temperature light sources radiate light because of their (relatively) high temperatures. Each hot body emits energy and if it is sufficiently hot, the portion of the energy is emitted in the visible region of the spectrum. Luminescent light sources
The Sun is the major source of light for the earth. The sun is a massive ball of fire, at the centre of which nuclear fusion produces massive energy. This energy comes out as heat and light.
The source of solar power is energy carried by the electromagnetic waves radiated by the Sun. Most of this energy is carried by visible light and infrared (heat) radiation.
þ Describe the sources and effects of heat. þ Explain thermal expansion of solids, liquids and gases. þ Explore the effects and applications of expansion and contraction of solids.
Part I – Energy and its Uses. 2. Units and scales of energy use (PDF - 1.1MB) 3. Mechanical energy and transport (PDF) 4. Heat energy: Conversion between heat and mechanical energy (PDF ‑ 2.9MB) 5. Electromagnetic energy: Storage, conversion, transmission and radiation (PDF - 7.7MB)
Heat is the flow of energy from one object to another. This flow of energy is caused by a difference in temperature. The transfer of heat can change temperature, as can work, another kind of energy transfer that is central to thermodynamics.
