Science Behind Color Change

The science of color is sometimes called chromatics. It includes the perception of color by the human eye and brain, the origin in materials, color theory in art, and the physics of electromagnetic radiation in the visible range(that is, what we commonly refer to simply as light).
The color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Physically, objects can be said to have the color of the light leaving their surfaces, which normally depends on the spectrum of the incident illumination and the reflectance properties of the surface, as well as potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light or emit light themselves, which contribute to the color also. And a viewer's perception of the object's color depends not only on the spectrum of the light leaving its surface, but also on a host of contextual cues, so that the color tends to be perceived as relatively constant: that is, relatively independent of the lighting spectrum,viewing angle, etc. This effect is known as color constancy.
When a light wave with a single frequency strikes an object, a number of things could happen. The light wave could be absorbed by the object, in which case its energy is converted to heat. The light wave could be reflected by the object. And the light wave could be transmitted by the object. Rarely however does just a single frequency of light strike an object. While it does happen, it is more usual that visible light of many frequencies or even all frequencies are incident towards the surface of objects. When this occurs, objects have a tendency to selectively absorb, reflect or transmit light certain frequencies. That is, one object might reflect green light while absorbing all other frequencies of visible light. Another object might selectively transmit blue light while absorbing all other frequencies of visible light. The manner in which visible light interacts with an object is dependent upon the frequency of the light and the nature of the atoms of the object.

Change Color (Page 53)

Materials:

Red and Green cellophane
Flashlight
Black box with hole in one side
Red playing card
Banana
Green apple


1. Place the objects in the box. Place the green
cellophane over the top of the box and shine
a flashlight through the hole in the side.

* The banana and the apple both reflect
green light.

* The red playing card doesn't reflect
green light, so the red on the card
appears black.


2. Do the same thing, but use the red cellophane.

* The banana reflects the red light,but the apple doesn't.

* The card reflects all colors, so now it looks red.

(Sam and I tried this with another color of red and it didn't work, but she found this one and it worked perfectly).