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Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. [ 1 ] [ a ] Flames , the most visible portion of the fire, are produced in the combustion reaction when the fuel reaches its ignition point .
This energy is partially absorbed and scattered in the atmosphere, the latter process being the reason why the sky is visibly blue. [3] Much of the Sun's radiation transmits through the atmosphere to the surface where it is either absorbed or reflected. Thermal radiation can be used to detect objects or phenomena normally invisible to the human ...
By recording the attenuation of light for various wavelengths, an absorption spectrum can be obtained. In physics, absorption of electromagnetic radiation is how matter (typically electrons bound in atoms) takes up a photon's energy—and so transforms electromagnetic energy into internal energy of the absorber (for example, thermal energy). [1]
Light consists of electromagnetic radiation of different wavelengths. Therefore, when the elements or their compounds are heated either on a flame or by an electric arc they emit energy in the form of light. Analysis of this light, with the help of a spectroscope gives us a discontinuous spectrum. A spectroscope or a spectrometer is an ...
Halogen lamps with fused quartz envelopes are used as inexpensive UV light sources in the near UV range, from 400 to 300 nm, in some scientific instruments. Due to its black-body spectrum a filament light bulb is a very inefficient ultraviolet source, emitting only a fraction of a percent of its energy as UV, as explained by the black body ...
The relativistic Doppler effect causes a shift in the frequency f of light originating from a source that is moving in relation to the observer, so that the wave is observed to have frequency f': ′ = /, where v is the velocity of the source in the observer's rest frame, θ is the angle between the velocity vector and the observer-source ...
A wood fire at 1500 K puts out peak radiation at about 2000 nanometers. 98% of its radiation is at wavelengths longer than 1000 nm, and only a tiny proportion at visible wavelengths (390–700 nanometers). Consequently, a campfire can keep one warm but is a poor source of visible light. The effective temperature of the Sun is 5778 Kelvin. Using ...
The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires. [1] The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). [2] A fire naturally occurs when the elements are present and combined in the right mixture. [3]