write an essay on
scattering of light.
Answers
Explanation:
Scattering of light is the phenomenon in which light rays get deviated from its straight path on striking an obstacle like dust or gas molecules, water vapours etc. ... The colors we see in the sky are due to scattering of light.Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light.As a result light becomes diffuse, which serves to obtain an even lighting without hot spots or without angular coloring, which is highly desired for many applications. Moreover, photons are recycled to yield more red and yellow light. Thereby cost efficiency is improved, and energy consumption is reduced
Answer:
When a beam of light travels through particles which are smaller than its wavelength, it is possible these particles scatter the light beam in a process known as Rayleigh scattering. This process is visible everyday whenever sunlight is scattered by the Earth’s atmosphere. As sunlight is composed of different visible wavelengths of light – mainly Red, Orange, Yellow, Green, Blue, Indigo and Violet; ROYGBIV – not all sunlight has the same probability of being scattered.
It is possible to determine the amount of Rayleigh scattering that the different visible wavelengths in sunlight experience by calculating the intensity of the individual scattered wavelengths. The intensity of light scattered by small particles (I) depends on the intensity (I0) and wavelength (λ) of the light source, the distance of the light source from the particle (R), the scattering angle (θ), the refractive index of the particle (n), and the diameter of the particle (d). The relationship between these variables is illustrated in the following equation:
I = I_0 frac{ 1+cos^2 theta }{2 R^2} left( frac{ 2 pi }{ lambda } right)^4 left( frac{ n^2-1}{ n^2+2 } right)^2 left( frac{d}{2} right)^6(Seinfeld & Pandis , 2006)
1.1 Mid-day
When the Sun is directly overhead, all the wavelengths of light originating from it travel the same distance from the Sun and through our atmosphere and are scattered by the same medium (nitrogen and oxygen molecules). Hence, I0, R, θ, n and d remain constant and the above equation can be simplified into:
With this equation, it can be seen that the intensity of scattered light is inversely proportional to the fourth power of a light’s wavelength and that the shorter a light’s wavelength, the more intensely visible it is.
Hence, as GBIV light (400nm to 500nm) have shorter wavelengths compared to ROY light (570nm to 700nm), GBIV light is more intensely visible to us.
Due to the shorter wavelengths of GBIV light, they also have higher chances of encountering atmospheric molecules than the ROY light and getting scattered by it, as shown in the figure below.
Although scattered light continues travelling in a random direction, a greater proportion of GBIV than ROY light reaches our eyes because GBIV wavelengths are shorter and more easily scattered. However, as our eyes detect the blue component in GBIV light that has been scattered the easiest (Leong, 2006), we see the mid-day sky as blue in colour.