China
Africa
Explore chapters and articles related to this topic
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.
Nanosensor Laboratory
Published in Vinod Kumar Khanna, Nanosensors, 2021
Diffraction is the change in the directions and intensities of a group of waves after passing by an obstacle or through an aperture, the size of which is approximately the same as the wavelength of the waves. The diffraction limit of resolution on the wafer is xd=ηλNA
Radiation—ionising and non-ionising
Published in Sue Reed, Dino Pisaniello, Geza Benke, Kerrie Burton, Principles of Occupational Health & Hygiene, 2020
Electromagnetic waves travel in air and vacuum at the speed (v) of light, 3.0 × 108 m/s, and are characterised by their wavelength (l, or λ, in metres) and frequency (f, in cycles per second, or hertz (Hz)). Wavelength and frequency are inversely proportional.
A review on viscosity retention of PAM solution for polymer flooding technology
Published in Petroleum Science and Technology, 2022
Juan Du, Chunhong Lv, Xitang Lan, Jifeng Song, Pingli Liu, Xiang Chen, Qiang Wang, Jinming Liu, Guixian Guo
The essence of photodegradation is also a kind of free radical degradation. Its mechanism is to transfer the absorbed light energy to the susceptible bond in the polymer through the chromophore in the polymer, resulting in the fracture of C-C bond and the formation of free radicals (Mel’nikov and Seropegina 1996; Vijayalakshmi and Madras 2006). The photodegradation of polymer is the result of photon absorbing energy. The energy of photon is directly proportional to the wavelength. The lower the wavelength, the higher the energy (Luo, Xu, and Torabi* 2013; Shemer, Kunukcu, and Linden 2006). An important source of photons is the sun. Among all the light waves of the sun, the wavelength of infrared is greater than 700 nm, the wavelength of visible light is 400–700 nm, and the wavelength of ultraviolet light is below 400 nm (Caulfield, Qiao, and Solomon 2002). The bond strengths of C—C, C-H and C-N are about 340,420,414 kJ/mol, respectively, which can be destroyed by wavelengths of 325,250,288 nm, respectively. Therefore, sunlight has little effect on C-H and C-N bonds, but can destroy C-C bonds (Smith, Prues, and Oehme 1997). Figure 5 shows the chain breaking mechanism of sunlight on C-C. S.P. Vijayalakshmi et al. studied the degradation of PAM at 266 nm wavelength using a pulsed Nd:YAG laser, followed the change of molecular weight during the degradation process by gel permeation chromatography, and found that the average molecular weight of PAM decreased by about 66% under 45 minutes of irradiation (Vijayalakshmi, Senapati, and Madras 2005).
Optimization of microalgae growth for biofuel production using a new empirical dynamic model
Published in Biofuels, 2021
Ibifubara Humphrey, Michael A. C. Chendo, Abdulahi N. Njah, Dike I. Nwankwo
According to Max Planck’s electromagnetic theory, light, which appears to be in a continuous range of frequencies or wavelengths, is actually emitted in separate packets of energy, called quanta, which can only take on certain discrete values. As such, the energy emitted is inversely proportional to the wavelength of light. This implies that shorter wavelengths have higher energy, whereas longer wavelengths have lower energy per photon (a particle representing a quantum of light). The wavelength of magenta light is 400 nm, that of blue light is 470 nm, and that of red light is 660 nm. In effect, a photon of magenta light has more energy than one of blue light, which in turn has more energy than a photon of red light; hence, magenta light photons produce better microalgae growth than did the sunlight, white light, blue light and red light by the end of the cultivation.
Study on the effects of denier and shapes of polyester fibres on acoustic performance of needle-punched nonwovens with air-gap: comparison of artificial neural network and regression modelling approaches to predict the sound absorption coefficient of nonwovens
Published in The Journal of The Textile Institute, 2019
Madaswamy Ramamoorthy, Raju Seenivasan Rengasamy
As known, the sound absorbers have low and high sound absorption at low and high frequencies, respectively. In general, energy dissipation is high when the maximum particle velocity is taking place, that is, sound absorption is high at high frequencies. Sound absorption at low frequencies can be improved either by increasing the thickness of sound absorbers and providing air-gap between the sound absorber and solid-backing. The wavelength decreases with increase in frequency. For instance, wavelengths corresponding to frequencies of 50 Hz is 6.86 m, 100 Hz is 3.43 m, 250 Hz is 1.37 m, 500 Hz is 0.69 m, 1000 Hz is 0.34 m, 2000 Hz is 0.17 m, 4000 Hz is 0.09 m and 6300 Hz is 0.05 m. Hence, high frequencies having shorter wavelengths can easily penetrate into the absorbers and consequently, there is a high chances of acoustic energy dissipation compared to sound with low frequencies (Tascan & Vaughn, 2008). Moreover, the propagation of low frequency and high frequency sound waves are determined by viscosity and inertia, respectively (Fahy, 2001). The sound absorption at low frequencies are controlled by the stiffness reactance of air in the material. However, it can be enhanced by providing an air-gap between the porous material and solid-backing (Shoshani & Yakubov, 1999).