White light appears colorless, but it is actually made up of all the colors of the visible light spectrum. The visible light spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. The electromagnetic spectrum encompasses all frequencies of electromagnetic radiation, ranging from radio waves to gamma rays. Visible light, the portion human eyes can detect, is just a small part of the entire electromagnetic spectrum.
The visible light spectrum consists of light with wavelengths ranging from about 380 nanometers (violet) to about 740 nanometers (red). Within this range, there are 7 distinct colors – red, orange, yellow, green, blue, indigo, and violet. When all these colors with their wavelengths are combined together, they make white light. So in that sense, white light is made up of 7 main colors.
The Visible Light Spectrum
The visible light spectrum can be demonstrated with a prism or diffraction grating which splits white light into its constituent colors. As white light passes through a prism, the different wavelengths (colors) bend at slightly different angles because they are refracted differently. This separates out the colors and displays the visible spectrum.
The 7 main colors of the visible light spectrum are:
| Color | Wavelength (nm) |
|---|---|
| Red | ~700 |
| Orange | ~610 |
| Yellow | ~580 |
| Green | ~550 |
| Blue | ~475 |
| Indigo | ~445 |
| Violet | ~400 |
The visible colors occur because each wavelength interval stimulates different color photoreceptor cones in our eyes. Red light has the longest wavelength while violet has the shortest. The other colors fall in between.
Additive Color Mixing
When all the wavelengths of the visible spectrum are combined together in equal amounts, they produce white light. This is known as additive color mixing, because combining wavelengths of light adds to produce a new color sensation.
The primary colors of additive color mixing are red, green and blue. This means combinations of different intensities of only red, green and blue light can produce all other colors. This principle is used in LED and LCD screens to produce colors by mixing red, green and blue pixels in different intensities.
When red, green and blue are combined at full intensity, the result is white light. So in displays, white is made by mixing 3 primary additive colors rather than 7 distinct colors.
The Rainbow and ROYGBIV
Many children are taught that the colors of the rainbow are ROYGBIV – red, orange, yellow, green, blue, indigo, violet. This is a handy mnemonic for remembering the sequence of hues in the visible spectrum. But rainbows are actually a continuous distribution of wavelengths across the spectrum with no strict boundaries between the colors.
Rainbows are produced when sunlight interacts with water droplets and becomes dispersed into its spectrum of colors. The wavelengths bend at slightly different angles to produce the rainbow arc with red on the outside and violet on the inside. Rainbows demonstrate how white sunlight is composed of the visible color spectrum.
So while ROYGBIV provides a useful way to remember the order of colors in the visible light spectrum, rainbows don’t actually have 7 distinct color bands.
Other Spectrums with 7 Colors
While the visible light spectrum is often said to have 7 colors, other color systems also use 7 colors:
| Color System | 7 Colors |
|---|---|
| Traditional RYB pigment mixing | Red, yellow, blue, orange, green, purple, black |
| Traditional art color wheel | Red, orange, yellow, green, blue, purple, black |
| Newton’s color wheel | Red, orange, yellow, green, blue, indigo, violet |
The RYB system is used in pigment and paint mixing, while the traditional color wheel shows relationships between hues. Newton also proposed 7 named colors in his color circle based on the musical scale.
So the idea of 7 main colors extends beyond just the visible light spectrum. Many color systems have adopted 7 as a key number of main hues.
Other Facts About White Light
Here are some other interesting facts about white light:
– White light can be created by combining the 3 primary paint pigments of red, blue, and yellow. This is known as subtractive color mixing as pigments subtract wavelengths to produce colors.
– The sun’s light appears white because it emits a broad continuous spectrum of wavelengths across the visible range. This combining of all visible wavelengths makes sunlight appear white to us.
– White LED light is produced by combining blue LED light with a yellow phosphor coating, rather than directly producing white light. This mixes blue and yellow to yield white.
– White light can be broken down into its spectrum by water droplets (rainbow), prisms, diffraction gratings ruled glass, and other optical dispersive elements. Different wavelengths refract at different angles.
– Not all white light sources have an equal intensity spectrum. Blue-heavy fluorescent lights will render colors differently compared to yellow-heavy incandescent bulbs.
– White is not technically a spectral color with its own specific wavelength. It results from uniform mixing of visible wavelengths.
Conclusion
While white light appears colorless, it is actually composed of the entire visible light spectrum wavelength range of about 380-740 nanometers. The visible spectrum is commonly broken down into 7 main color bands – red, orange, yellow, green, blue, indigo, violet. Combining these 7 distinct colors together in the right proportions produces white light. So in this sense, white light is made up of 7 main colors. Other color systems like RYB and artistic color wheels also reinforce the idea of 7 key colors making up the diversity of hues. So the notion that 7 colors can combine to create white light is grounded in scientific fact and artistic color theory.
