Light and Color

Objective S8P4. Explain how the human eye see objects and colors in terms of wavelengths. What Does It Mean? Explain how light with different properties are detected by the human eye as different colors.

Light and Matter Light interacts in 3 ways when it strikes matter-it can be reflected, absorbed, or transmitted. Transmission- the passing of light through matter. We see the transmission of light all of the time.

Light is transmitted, reflected, and absorbed when it strikes the glass in a window.

Types of Matter Matter that allows light to pass through (transmit) easily is transparent. Examples: air water, and glass. You can see objects clearly when you see them through transparent objects.

Translucent- matter that transmits light but also scatters the light as it passes through the matter. Examples: wax paper, frosted shower doors, frosted light bulbs

Matter that does not transmit any light is- opaque. You cannot see through opaque objects. Metal, wood, and books are examples.

Colors of Objects Roy G. Biv The color of light is determined by the wavelength of the light wave. Red has the longest wavelength, violet has the shortest wavelength, and the other colors have wavelength in between. Roy G. Biv The color that an object appears to be is determined by the wavelengths of light that reach your eyes. Your brain converts the light that has reached your eyes into electrical impulses and interpreted by the brain as colors.

Colors of Opaque Objects When white light strikes a colored opaque object, some colors of light are absorbed and some are reflected. Only the light that is reflected reaches your eyes and is detected. When white light hits a strawberry, only red light is reflected. All other colors are absorbed.

What colors are reflected by the cow shown at right? The white hairs on the cow’s hide appear white because all the colors of light are reflected. The black hairs on absorb all of the colors of light and reflect none back to your eyes.

Colors of Transparent and Translucent Objects When you look through a colored transparent or translucent object, you see the color of light that was transmitted through the material. The bottle is green because the plastic transmits only green light.

Mixing Colors of Light White light is a combination of 7 colors of light. However, we can also get white light by mixing 3 colors of light- red, blue, and green. Red, blue, and green are known as the primary colors of light.

Mixing Colors of Pigment You cannot mix red, blue, and green paint to make white paint. The difference in mixing light and mixing paint is due to paint containing a pigment. A pigment is a material that gives a substance its color by absorbing some colors of light and reflecting others. Almost everything contains pigments. Examples: chlorophyll and melanin. Chlorophyll gives plants their green color and melanin gives us our skin color.

http://www.brainpop.com/science/energy/color/zoom.weml http://www.brainpop.com/science/energy/light/zoom.weml

Review Questions Which of the following colors of light has the shortest wavelengths? a. Red b. Yellow c. Blue d. Violet

Which is the BEST description of a translucent material? a. It absorbs almost all of the light that strikes it. b. It transmits some light waves, scatters others. c. It does not transmit light waves. d. It reflects almost all of the light that

Why do you see a banana as yellow? a. The banana absorbs wavelengths for most colors of light, while reflecting wavelengths for yellow light. b. The banana absorbs wavelength for yellow light, while wavelength for other colors of light are reflected. c. The banana absorbs only yellow wavelength of light, and the colors of all other wavelengths are transmitted. d. The banana does not absorb wavelength for any color of light.

Answers 1. d; violet (Roy G Biv) 2. b; translucent materials produce a fuzzy image because some light is transmitted and other light is scattered. 3. a; the banana reflects the color yellow. You must have light reflected in order to see.