Light and Color - Mission LC9 Detailed Help

Two spotlights of equal intensity illuminate a 'white' screen with red and blue light. A person stands between the spotlights and the screen in such a manner as to cast two colored shadows upon the screen. The two shadows overlap, producing several colored regions. Indicate the color of each region.


 
Light and Shadows
Shadows are projected onto a surface when an object is positioned between the light source and the surface. In such instances, light is projected onto part of the surface but not onto all the surface. An outline of the object is formed on the part of the surface that light does not reach.


 
Many students of physics have seen a diagram similar to the one shown at the right. The diagram depicts three circles colored with the primary colors of light - red, green and blue. The primary colored circles overlap to produce other colors of light, known as the secondary colors of light: cyan (C), magenta (M) and yellow (Y). For instance, the red and green light combine to form yellow light. Green and blue light combine to form cyan light. Blue and red light combine to form magenta light.


 
Two shadows will be cast onto the screen - one for each light. That is, there will be one region on the screen - in the outline of the person - where blue light does not reach. And there will a second region on the screen - in the outline of the person - where red light does not reach. Some logical thinking will help you determine which shadow is which. The two shadows overlap. This overlap region is a region where neither the red nor the blue light reach; it is a dark region that is not illuminated by light at all. Outside of these shadows, both red and blue light will combine to produce a third color (use the color wheel in the Dig That Diagram section).


 

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