Light Sources and the Particle Nature of Light
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As the nineteenth century was coming to a close, Newtonian mechanics could explain and predict the motion of objects ranging in size from pebbles to planets while Maxwell’s theory of electromagnetism unified electricity, magnetism, and optical phenomena.
Glossary of Terms
Temperature on a scale that begins at absolute zero and measures temperature in kelvins (K). Celsius temperature is converted to absolute temperature by adding 273 K.
An ideal absorber and emitter of light.
Model of the atom in which electrons move in stable orbits around the nucleus.
Light in which all photons have the same phase and wavelength (such as laser light) .
The temperature of the blackbody with the closest spectral energy distribution to a given light source.
Measure of the power efficiency (lumens per watt) of a light source.
Unit of energy equal to the energy that an electron would acquire traveling from the negative to positive terminal of a 1-volt battery.
Ratio of the radiant energy from a nonideal surface to that of a blackbody at the same temperature.
Absorption of light and subsequent reemission at a longer wavelength.
Measure of the light intensity striking a surface in lumens/m2 (lux) .
Measure of the radiation intensity on a surface.
Unit of energy in SI system.
One degree on the absolute temperature scale.
Coherent monochromatic light source that utilizes the stimulated emission of radiation.
A very efficient semiconductor light source used especially in outdoor displays, radios, TVs, home appliances, and automobile tail lights.
Unit for measuring luminous flux or output of light sources.
Absorption of energy and emission of light; includes fluorescence and phosphorescence.
Radiant flux scaled according to the sensitivity of the eye at each wavelength.
Light-emitting device having dimensions on the order of 10 to 100 nm.
Absorption of light and delayed emission at longer wavelength.
Illuminance meter used by photographers, illumination engineers, and others.
Measurement of energy content in the visible portion of the electromagnetic spectrum.
A particle of light having an energy hc/λ.
A condition in which more atoms are in the higher energy state than in the lower one (a nonequilibrium condition).
A nanoscale semiconductor that emits light in wavelengths that are determined by its size.
Measurement of radiant energy of electromagnetic radiation.
A photon triggers an atom to emit a photon of the same wavelength (as in a laser).
Unit of power in SI system.
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