Optical mixing using a diffusion filter
STEAM EXERCISE
Details:
Middle-high school and up
Time: 5 minutes
Learning Outcome: Recognize that as a source becomes smaller and smaller, at some point the sources will no longer be seen as separate, and their combined light will generate a new colour perception.
Colour Concepts: Optically mixed colours produce new colour perceptions.
Materials:
Diffusion filter from Colour paddle set (can also use wax paper)
Instructions:
Look at the grids below (or printed on handout) through the diffusion filter. What do you notice? Describe the colours you see.
How does the colour change when you look at the smaller grids?
Figure 1. Examples of diffusion filters.
Figure 2. Grids for viewing through diffusion filter.
Vocabulary:
Questions & observations:
How do the different blues used in the grid pattern affect the optically mixed colour you see?
At what point does the appearance of the grid go from seeing the individual squares in the grid to seeing an optically blended colour?
More to explore:
Make your own grids. Try different coloured grids.
What’s going on?
A diffusion filter diffuses or changes the directions of light beams as they pass through the filter. When we look through a diffusion filter, the image becomes blurred. Using the diffusion filter in this exercise allows the light from the blue and yellow (or cyan and yellow) coloured areas in the grid to blend optically in our eyes.
Optical mixing is an example of the additive mixing process. As a source becomes smaller and smaller, at some point the sources will no longer be seen as separate, and their combined light generates a new colour perception.
This type of optical mixing is also called partitive mixing or averaging.
Find out more:
See the glossary entry on the different types of the additive mixing processes.
