Color Addition and Subtraction - help6

The color appearance of an object depends upon the colors (wavelengths) of light that are reflected by the object to the observer's eyes. Objects can interact with the incident light to absorb one or more primary colors of light. This is called color subtraction. The colors that are not absorbed or subtracted from the incident light are reflected to the observer's eyes.

The Fundamentals
This Concept Builder will demand that you understand both color addition and color subtraction. The graphic at the right is a great starting point. It shows the three primary colors of light - red, green, and blue. It also shows the three secondary colors of light - cyan, magenta, and yellow.

Now as you approach a question like this one, you think in terms of primary light colors. For instance, if a person observes an object to appear magenta, then red + blue light are being reflected to the observer's eye. Similarly, a cyan appearance of an object indicates that the object is reflecting blue + green light to the eye.


The Incident-Absorbed-Reflected Model
A useful model for analyzing color questions is the incident-absorbed-reflected model. The model suggests that a successful analysis includes three steps ... with each step involving the answering of a question. Those steps or questions are ...

1. What primary color(s) of light are incident upon the paper?
2. Of the primary light colors that are incident, which color(s) is/are absorbed by the paper?
3. Of the primary light colors that are incident, which color(s) is/are reflected by the paper?

The absorbed light color(s) is/are subtracted from the incident light colors. This is called color subtraction. Once the subtraction process is complete, the result is the reflected light color. It is the reflected light color that reaches the observer's eye and determines the color appearance of the shirt.


Applying the Principles
In this question, there are two primary incident colors of light. The appearance of the paper corresponds to one of those primary colors of light or to black. The black appearance results when no light reflects to the eye. Both primary colors are absorb in this case. The non-black appearance of the paper results when one of those incident light colors are reflected. The appearance of the paper is determined by the reflected light color. It is the other incident light color that is getting absorbed.