Question

Sunlight appears white. However, rainbows, sunburn and the ability to see colors tell a different story.Explain what each of these tells us about the suns radiation and what property determines different colors.

Answer 1

A) Sunlight basically consists of a combination of light of different wavelengths. Each of these wavelengths correspond to each of the colors of the rainbow. For example, red light has the longest wavelength. This is followed by orange, then yellow, green, blue and indigo. Violet has the shortest wavelength. These wavelengths (750 nm  to 400 nm) constitute the visible colors. All these light components of different wavelengths combine together to become the color white.

b) When this sunlight passes through droplets of rain, it gets refracted and that is what breaks up the white light into individual colors of the rainbow, just how light passing through a glass prism gets broken down into its individual seven colors.

c) Different objects have the ability to absorb different wavelengths of light. For example, glass absorbs light of all wavelengths except those between 560-520nm, which corresponds to green light. So it reflects the green light and thus, our eyes see  grass as green in color.

d) Light of wavelength below  400 nm (ultraviolet) and above 750nm (Infrared) are not visible. However, they exist in the sun's radiation. Ultraviolet rays are very harmful and responsible for causing sunburn and some types of skin tumors. Infrared light is also harmful and can cause premature wrinkling of skin.