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Activity

Coloured shadows

Summary: 
Shine red, blue and green lights on a white wall. Turn the lights on and off in different combinations to create different coloured shadows and overlapping shapes.
Science content (2016 curriculum): 
Physics: Light and Sound (1)
Science topic (2005 curriculum connection): 
Physical Science: Light and Sound (grade 4)
Lessons activity is in: 
Materials: 
  • Three light bulbs in holders - red, blue and green. Can also use flashlights covered with coloured acetate
  • White wall
Procedure: 

Turn the lights on and of in different combinations while holding a hand up to create shadows.
Experiment to find out what is going on.

With one bulb we get the light coming from it showing on the white wall. If our hand is in the way, we block the light and there is a dark shadow.
With two colours we make a new colour (additive colours of light). Our hand blocks one, leaving the other colour showing in its shadow.
cyan is blue and green
magenta is blue and red
yellow is red and green (red and green receptors in our eye are stimulated by yellow)
With three colours, we make almost white. Our hand blocks one, leaving the mixture of the other two colours in its shadow. We get dark where all three shadows overlap.

Grades tested: 
Gr K
Gr 1
Gr 3
Gr 4
Gr 5
Teacher: 
Ingrid
Teaching site: 
General Gordon Elementary Science Club
ingridscience afterschool
Science Workshop for Destination Imagination