Many of us have witnessed a rainbow, a common natural occurrence, when the sun begins to shine after a period of rain. The rainbow comprises a spectrum of light that appears in the sky as a result of light reflection, refraction, and dispersion in water droplets. The seven main colours we see in rainbow are red, orange, yellow, green, blue, indigo and violet. However, we never see colours like black, white or grey in rainbows.
According to a report published in Science Report, "but there are two colours we would never see in a rainbow - black and white. Black is the absence of colour - it's what we see when there's no light at all. On the other hand, white is a combination of all the colours together. When light is refracted by raindrops, it separates the white light out into the visible spectrum, meaning it is no longer white. Grey is a mix of black and white, and as we can't ever see black and white in a rainbow, we also can't see colours made by mixing them."
According to the National Geographic, When sunlight hits a rain droplet, some of the light is reflected. The electromagnetic spectrum is made of light with many different wavelengths, and each is reflected at a different angle. Thus, spectrum is separated, producing a rainbow. Red has the longest wavelength of visible light, about 650 nanometers.
The media outlet further explains that "a rainbow is an optical illusion-it does not actually exist in a specific spot in the sky. The appearance of a rainbow depends on where you're standing and where the sun (or other source of light) is shining."
