Waves

How do we see color?

8-6.7

Standard 8-6.7

• Explain how the absorption and reflection of light waves by various materials result in the human perception of color.

Prior Knowledge

• What are the colors that make up light?

• Why do objects have color?

Absorption

• As we have learned before, most objects absorb some of the frequencies of the spectrum but reflect other frequencies.*

• If a material absorbs a certain frequency of light, that frequency will not be reflected, so its color will not be seen by the observer.*

Light Waves

• The absorption and reflection of light waves by various materials results in human perception of color as follows:

•  Most materials absorb light of some frequencies and reflect the rest.

Absorption & Reflection

• If a material absorbs a certain frequency of light, that frequency will not be reflected, so its color will not be perceived by the observer.

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• If the material does not absorb a certain frequency of light, that frequency will be reflected, so its color will be perceived by the observer.

Absorption

• The frequency that is reflected makes the color for that object.*

• Red apples are red because the apple’s skin does not absorb the red frequency.

Absorption

• Objects that reflect all frequencies of color are WHITE.**

• Objects that absorb all frequencies of color are BLACK.**

Primary Colors

• The human eye can distinguish thousands of different colors.

• There are 3 primary colors…– RED, BLUE, & GREEN

• Light of almost any color can be made from mixing different amounts of the primary colors.

Primary Colors

• The colors on this slide are combinations of the primary colors.

Colors

• The colors that we see depend on 2 things.*– 1. the color of light that is shined on the

object.– 2. the color of light that is reflected by the

object.

For example: if an object reflects red wavelengths and absorbs all others, the object will appear red in color.

Color Filters

• Color filters allow only certain colors of light to transmit through them.**

• They absorb or reflect all other colors.**

Color Filters

• For example:– A blue filter only transmits blue light.– Objects seen through a blue filter will look

blue if the objects reflect blue.– Objects of other colors will appear black

because the other color frequencies are being absorbed by the filter.