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The main source of natural light on Earth is the Sun. Historically, another important source of light for humans has been fire , from ancient campfires to modern kerosene lamps . With the development of electric lights and power systems , electric lighting has effectively replaced firelight.
This is a list of sources of light, the visible part of the electromagnetic spectrum.Light sources produce photons from another energy source, such as heat, chemical reactions, or conversion of mass or a different frequency of electromagnetic energy, and include light bulbs and stars like the Sun. Reflectors (such as the moon, cat's eyes, and mirrors) do not actually produce the light that ...
Again the system relaxes vibrationally in the new spin state and eventually emits light by phosphorescence. Most photoluminescent events, in which a chemical substrate absorbs and then re-emits a photon of light, are fast, in the order of 10 nanoseconds. Light is absorbed and emitted at these fast time scales in cases where the energy of the ...
An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue (apart from the area around the Sun which appears white because the light is not scattered as much). The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum.
The emission spectrum of a light source varies depending on the light generating mechanism. Thermal sources such as incandescent bulbs produce electromagnetic radiation over a broad and continuous range of wavelengths, including infrared and ultraviolet. A black body radiator is the idealized version of a thermal source. As the temperature of a ...
The optical atmospheric window is the optical portion of the electromagnetic spectrum that passes through the Earth's atmosphere, excluding its infrared part; [10] although, as mentioned before, the optical spectrum also includes the IR spectrum and thus the optical window could include the infrared window (8 – 14 μm), the latter is ...
Photosensitizers utilize light to enact a chemical change in a substrate; after the chemical change, the photosensitizer returns to its initial state, remaining chemically unchanged from the process. Photoinitiators absorb light to become a reactive species, commonly a radical or an ion, where it then reacts with another chemical species. These ...
There are no actual daylight light sources, only simulators. Constructing a practical light source that emulates a D-series illuminant is a difficult problem. The chromaticity can be replicated simply by taking a well known light source and applying filters, such as the Spectralight III, that used filtered incandescent lamps. [22]