why do we see red and green light as yellow

Roses are red and violets are blue, but we only know that thanks to specialized cells in our eyes called cones. When light hits an object say, a banana the object absorbs some of the light and reflects the rest of it. Which wavelengths are reflected or absorbed depends on the properties of the object. For a ripe banana, wavelengths of about 570 to 580 nanometers bounce back. These are the wavelengths of yellow light. When you look at a banana, the wavelengths of reflected light determine what color you see. The light waves reflect off the banana s peel and hit the light-sensitive retina at the back of your eye. That s where cones come in.


Cones are one type of photoreceptor, the tiny cells in the retina that respond to light. Most of us have 6 to 7 million cones, and almost all of them are concentrated on a 0. 3 millimeter spot on the retina called the fovea centralis. Not all of these cones are alike. About 64 percent of them respond most strongly to red light, while about a third are set off the most by green light. Another 2 percent respond strongest to blue light. When light from the banana hits the cones, it stimulates them to varying degrees. The resulting signal is zapped along the optic nerve to the visual cortex of the brain, which processes the information and returns with a color: yellow.


Humans, with our three cone types, are better at discerning color than most mammals, but plenty of animals beat us out in the color vision department. Many birds and fish have four types of cones, enabling them to see ultraviolet light, or light with wavelengths shorter than what the human eye can perceive. Some insects can also see in ultraviolet, which may help them see patterns on flowers that are completely invisible to us. To a bumblebee, those roses may not be so red after all.
Light is a kind of energy called electromagnetic radiation.


There are many different forms of electromagnetic radiation, such as radio waves, microwaves, ultraviolet rays, and X-rays. Each form is characterized by a different wavelength. For example, radio waves can be several miles long, while gamma rays are smaller than atoms. The light that we see visible light falls somewhere in the middle of this "electromagnetic spectrum. " Visible light may be a tiny part of the electromagnetic spectrum, but there are still many variations of wavelengths. We see these variations as colors. On one end of the spectrum is red light, with the longest wavelength.


Blue or violet light has the shortest wavelength. White light is a combination of all colors in the color spectrum. It has all the colors of the rainbow. Combining primary colors of light like red, blue, and green creates secondary colors: yellow, cyan, and magenta. All other colors can be broken down into different combinations of the three primary colors. Objects appear one color or another because of how they reflect and absorb certain colors of light. For example, a red wagon looks red because it reflects red light and absorbs blue and green light. A yellow banana reflects red and green light, and absorbs the rest.

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