How do we see different colors?

in #sciencelast year

In order to know about colors, it is first necessary to explain what light is. Light is a type of energy. Light consists of electromagnetic radiation. Electromagnetic radiation has the properties of both particles and waves. You could also say that it is a wave of both electricity and magnetism. It is made up of radiation particles which are called photons. These are small packets of energy.

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Photons consist of different energies, not all photons are in the Visible Spectrum so the human eye can only see light at a wavelength of 400 to 700 nanometers. The visible spectrum begins at 400 nanometers of violet photons and ends at 700 nanometers of red photons, so electromagnetic waves above 700 nanometers are called infrared. More than that wavelengths include Radars, FM, TV, Shortwave and AM.

Waves below 400 nanometers are called ultraviolet waves and more low wavelength rays include X-rays and cosmic rays. We are able to see only a very small portion of the spectrum of electromagnetic waves (approximately 0.0035%). We cannot see ultraviolet and infrared lights because our eyes do not have the ability to see wavelengths less than 400 nanometers and more than 700 nanometers. These are sensors in our retina that sense the wavelength of only such light.

The photons of the Visible Spectrum have the highest intensity of light coming from the Sun. As the sunlight enters the Earth's Atmosphere, the UV light is reflected from the Ozone Layer and the rest of the light which appears to us as white reaches the solid surface of the earth. This white light is a combination of lights of all colors. If the prism is placed in front of this light, then all these colored lights appear to be different from each other. The wavelengths of all colored lights are different from each other. There are basically three colors: red, blue and green. All the other colors that we see are formed by mixing different amounts of the same three colors.

Whenever light falls on an object, the reflected light hits our eye and the reflected light is reflected on our retina. In the form of signals, the optic nerve reaches the visual cortex of our brain where the information received, creates an image and we can recognize it.

Colors are also related to the retina. The normal human eye has 6 to 7 million cones that are used to recognize different colors. In a normal human being, 64% of these cones respond to red color, while 33% is for green and only 2% is for blue. In some birds and fish these cones are of four kinds which makes them able to see ultraviolet light and all these 6-7 million cones occur in only 0.3 mm part of our retina. When light of different colors reach the retina, this colored part has a different effect depending on the wavelength which reaches the brain with the help of optic nerve where colors are used to identify the difference.

The reason why different colored objects have different colors is that they absorb most of the light that falls on them and the rest that they reflect is the color of the object we see. If we talk about matter, the unit of matter is the atom. Atoms themselves do not have any kind of color. The thing that gives them color is "electron".

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Molecules usually have the properties of colors. When light is applied to a molecule, the electron in its outer shell absorbs light and then emits some of that light, and this part of the light emitted is the color of the molecule. If the electron emits the same amount of light, atoms / molecules will appear transparent if light is absorbed.

Light does not pass through many objects such as fine paper, wall, cloth, but it passes easily through glass which is a solid object. The reason given above is that when light falls on glass, the electrons of the existing atoms absorb this light and get excited and again the same amount of energy, that emits photons and returns to the ground state, due to which light appears to pass through the glass and due to this absorption and emission, the speed of light slows down inside the glass. In this way, if light does not return after hitting a solid object, black color is seen because this color is capable of absorbing all colors while white color is visible due to reflecting light of all colors.

Thank you for reading! Stay Safe!👋😌

Reference:

1- https://www.sciencenewsforstudents.org/article/understanding-light-and-other-forms-of-energy-on-the-move

2- https://en.wikipedia.org/wiki/Cone_cell

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