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Application
Published in Benny Raphael, Construction and Building Automation, 2023
Since light consists of electromagnetic energy that flows at a finite speed c, we can compute the amount of energy flowing per unit time, that is, the power in Watts (Joule per second). However, not all electromagnetic energy is visible to us as light. Only electromagnetic waves having a certain wavelength can be received by our eyes and perceived as visible light. This range is called the visible spectrum and consists of wavelengths from 380 to 800 nanometers. Different colors have their ranges of wavelength; violet is from 380 to 450 nanometers on one end, and at the other end of the spectrum, red has wavelengths from 625 to 800 nanometers. Our eyes are more sensitive to certain colors. For example, with the same amount of electromagnetic power, green appears brighter than other colors. Therefore, electromagnetic power (Watts) is not a good quantity to measure the perceived brightness of light. We need another unit that takes into account the sensitivity of the eye to different wavelengths.
Borate Phosphors for Solid-State Lighting
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
The light source is expected to cover the entire visible spectrum. Hence, a good source should have a high CRI value. If the CRI value for a light source is more than 70, then it is acceptable. The CRI value of the convention incandescent lamp is 95 but luminous efficacy is very low. The cool, white fluorescent lamp has a CRI of 62, whereas in the case of a fluorescent lamp coated with tri-colour emitting phosphors CRI increases to more than 80. There is always a trade-off relationship between luminous efficacy and the colour-rendering index. The increased CRI is at the cost of a decrease in luminous efficacy. The human eye is most sensitive at 555 nm. Hence, luminous efficacy of radiation is highest for monochromatic radiation of 555 nm wavelength. However, for good CRI values, broadband spectral distribution throughout the visible spectrum is desirable. Hence, generally, balance is adopted between the two depending on the application areas [21,65,68,69].
Microalgae for Removing Pharmaceutical Compounds from Wastewater
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Eliana M. Jimenez-Bambague, Aura C. Ortiz-Escobar, Carlos A. Madera-Parra, Fiderman Machuca-Martinez
Light is very important in the photosynthesis process and the production of new biomass. It is a limiting factor of microalgae development and effective behavior of microalgae-based systems. In photosynthesis, artificial light or sunlight is converted in chemical energy through pigments such as chlorophylls (Chlorophyll-a being the main pigment) and carotenoids that are absorbed in specific wavelengths of the visible spectrum. The absorption range, known as photosynthetically active radiation (PAR), is the amount of useful energy for the photosynthesis process. PAR is located within the 400 to 700 nm solar spectrum wavelength (Righini and Grossi Gallegos 2005).
A common type of commercially available LED light source allows for colour discrimination performance at a level comparable to halogen lighting
Published in Ergonomics, 2019
Sara Königs, Susanne Mayr, Axel Buchner
Light sources based on light emitting diodes (LEDs) have become superior to other conventional light sources such as incandescent, halogen, or fluorescent lamps in terms of lifetime and efficiency (Chang et al. 2012). The efficiency of a light source is characterised by its luminous efficacy which is defined as the ratio of the luminous flux to the electrical power consumption (Boyce 2014), measured in lumens per watt (lm/W). Apart from luminous efficacy and lifetime, LED-based light sources differ from other conventional light sources in their spectral power distribution. The spectral power distribution reflects the intensity of emitted radiation at each wavelength (Houser et al. 2016). Radiation in the wavelength range from 380 to 780 nm (the visible spectrum) leads to a response of the human visual system (Boyce 2014) and thus triggers the perception of colour; for normal observers short wavelengths appear as blue light, medium wavelengths as green light, and long wavelengths as red light (Houser et al. 2016).