THE dispersal it is a optical phenomenon in which light is separated into its different Colors when refracted through some transparent medium, such as the Rainbow, prism and photographic lens. Dispersion occurs when the speed of propagation of light within a medium depends on the frequency of the electromagnetic wave.
Lookalso:What are primary colors?
In 1672 the English physicist Isaac Newton studied and elaborated theories on the mechanism of light scattering. Despite his corpuscular interpretation of light, Newton was able to explain that the White light was actually composed of all other colors and that these colors were relative to the frequencies (or wavelengths) of light.
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light refraction
THE refraction is the phenomenon in which light has its altered speed. This phenomenon may or may not be accompanied in a change in the path taken by the light that propagates through the medium. The measure of the change in the speed of refracted light can be calculated using a dimensionless coefficient called refractive index:
no - Refractive index
ç — Speed of light in vacuum (c = 3.0.108 m/s)
v — Speed of light in the middle (m/s)
The refractive index measures the reason between the speed of light in vacuum for the speed of light in a given medium, therefore, the refractive index module must always be greater than 1. A refractive index of 1 indicates that light moves through an optical medium at the same speed as it could travel in a vacuum.
In addition to directly affecting the speed at which light propagates within it, the refractive index, through the snell's law, indicates that the light beam may suffer a Detourangular in its trajectory. The greater the refractive index, the greater this angular deviation. Such law is described by the Mathematical Equation shown in the following figure:
no1 — Index of refraction of medium 1
no2 — Index of refraction of medium 2
if not1 — Sine of incidence angle
if not2 — Sine of refraction angle
The next image shows the light falling on medium 2 emerging from medium 1:
If you want to understand more about this optical phenomenon, check out our article: Refraction.
Lookalso: Discover the most incredible optical phenomena
white light decomposition
Because white light is composed of different light frequencies, and the refractive index is different for each of these frequencies, the angular deviation of light will also be different for each of them.
In this way, it will be possible to observe the electromagnetic spectrum after light propagates inside a prism and in other transparent media, as can be seen in the following image:
When light is refracted, it is possible to visualize its composition.
O refractive index it is proportional to the frequency of light and inversely proportional to its wavelength. This indicates that violet light, for example, must suffer a greater angular deviation than red light, since, for this component of light, the refractive index is higher:
Violet is the color that suffers the greatest angular deviation when refracted.
Rainbow Light Scattering
The rainbow is an optical phenomenon that originates from the scattering of light. This one comes up when there is a large number of water droplets in the air. White light enters the interior of these droplets and undergoes refraction, then undergoes a total internal reflection, and is finally refracted back into air.
The path taken by the light inside the droplet is long enough to observe the angular deviation between the different frequencies of white light.
The rainbow is formed by the scattering of light that passes through small droplets of water.
Want to know more about this optical phenomenon? Access our text: Rainbow.
Lookalso: What is the speed of light?
Light scattering experiment
Light scattering experiments are easy to drive and usually have low cost. If you want to do an experiment that allows you to visualize the scattering of light, we suggest you have: a prism of acrylic or glass and a collimated source, like a fluorescent lamp placed behind a screen with a small slit.
In a dark room, turn on the lamp and position the screen in front of it, at a distance where its light produces a line of light on the surface where the prism is located. Bring the prism together and rotate it, until you can see the dispersalgiveslight.
See too:Difference between phosphorescent and fluorescent lamp
light scattering
Light scattering is the phenomenon in which light incident on a particle is reissued in other directions, but with the same frequency.
However, there is the phenomenon of selective spreading. In this phenomenon, particles scatter, more efficiently, certain frequencies of light. In the case of atmospheric particles, these are highly efficient in spreading the frequencies referring to colors blue and violet. That's why our sky is blue.
Refraction of light in the atmosphere
Did you know that the color of a sunset has to do with the refraction of light?
THE light refraction in the atmosphere is why the sunset is orange. During sunset, the path that light travels until it reaches our eyes is greater, thus, the angular deviation of light is more noticeable.
Furthermore, the fact that scattering occurs only for blue and violet light makes the smaller frequencies such as red and orange are more present at long distances, as they travel over distances much larger.
By Me. Rafael Helerbrock
Would you like to reference this text in a school or academic work? Look:
HELERBROCK, Rafael. "White Light Scattering"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/a-dispersao-luz-branca.htm. Accessed on June 27, 2021.
