Search results
Results from the WOW.Com Content Network
Solar spectrum with Fraunhofer lines as it appears visually. In 1802, English chemist William Hyde Wollaston [2] was the first person to note the appearance of a number of dark features in the solar spectrum. [3] In 1814, Joseph von Fraunhofer independently rediscovered the lines and began to systematically study and measure their wavelengths ...
Using Wien's law, one finds a peak emission per nanometer (of wavelength) at a wavelength of about 500 nm, in the green portion of the spectrum near the peak sensitivity of the human eye. [3] [4] On the other hand, in terms of power per unit optical frequency, the Sun's peak emission is at 343 THz or a wavelength of 883 nm in the near infrared ...
The standard luminous efficiency function is normalized to a peak value of unity at 555 nm (see luminous coefficient). The value of the constant in front of the integral is usually rounded off to 683 lm/W. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function.
Solar spectrum with Fraunhofer lines as it appears visually. A material's absorption spectrum is the fraction of incident radiation absorbed by the material over a range of frequencies of electromagnetic radiation. The absorption spectrum is primarily determined [2] [3] [4] by the atomic and molecular composition of the material.
The Sun, with an effective temperature of approximately 5800 K, [14] is an approximate black body with an emission spectrum peaked in the central, yellow-green part of the visible spectrum, but with significant power in the ultraviolet as well. Blackbody radiation provides insight into the thermodynamic equilibrium state of cavity radiation.
The Sun produces radio emissions through four known mechanisms, each of which operates primarily by converting the energy of moving electrons into electromagnetic radiation. The four emission mechanisms are thermal bremsstrahlung (braking) emission, gyromagnetic emission, plasma emission, and electron- cyclotron maser emission.
The solar reflectance of green roofs varies depending on the plant types (generally 0.3–0.5). [32] Green roofs may not reflect as much as a cool roof but do have other benefits such as evapotranspiration which cools the plants and the immediate area around the plants, aiding in lowering rooftop temperatures but increasing humidity, naturally.
If the instrument is designed to measure the spectrum on an absolute scale rather than a relative one, then it is typically called a spectrophotometer. The majority of spectrophotometers are used in spectral regions near the visible spectrum. A spectrometer that is calibrated for measurement of the incident optical power is called a ...