Think about the waves in the ocean. They seem to roll forward. Sometimes the waves are wide and slow. At other times, the waves seem close together and they move quickly. Light moves in waves too. Some of the waves seem to move slowly with wider spaces between them. Others move more quickly with smaller spaces between them. The length of space between two waves is the wavelength. How quickly the waves move up and down is the frequency. The longer the wavelength – think of a slow, rolling wave – the lower the frequency.The shorter the wavelength – think of fast, choppy water – the higher the frequency. Color is part of light. Each color of the rainbow has a specific wavelength and frequency. Purple, for example, is a high frequency, short wavelength. Red is a low frequency, high wavelength.
- Humans cannot see every color (or wavelength) on the electromagnetic spectrum. We can’t see microwaves, X-rays, or radio waves but we know they’re there.
- The colors of the rainbow always go in the same order: red, orange, yellow, green, blue, indigo, and violet.
- When light falls on an object, some of the wavelengths are absorbed and some are reflected back. The color you see is the wavelength that is reflected back while all the other colors on the spectrum are absorbed.
- White is a combination of all colors. When you see white, all the wavelengths are being reflected. None are being absorbed.
- Black is the opposite of white. All the colors are being absorbed. Nothing is being reflected.
- Frequency: how quickly a wave goes up and down
- Wavelength: the distance between two waves
Question and Answer
Question: How are colors classified?
Answer: Red, yellow, and blue are additive or primary colors. You can make any other color by combining or adding these colors. Cyan, magenta, and yellow are subtractive colors. You can make other colors by removing these colors from white light.
Visit the Optics Society for hands-on color and light activities.