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Shadows HTML5

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Summary

Light rays travel in straight lines from the light source. Studying a shadow's shape is an important proof  of this characteristic of light. The light source here is supposed to be a « point source ».
The shadow of an object on a screen is the area of the screen which is not reached by rays from a light source.
A common misconception is that a light source creates a shadow behind an object. In fact, the source adds light to areas all around the shadow, and it is the resulting contrast that makes the shadow appear.
The form of the shadow depends on the relative positions of the source, the object and the screen.

Click and drag vertically the spotlight.

Learning goals

  • To illustrate that the shape of a shadow depends on the positions and shapes of three parameters: the light source, the object and the surface on which the light is shadow is cast.
  • To show that  the shadow cast is the portion of the screen that does not directly receive light from the source. (But this zone can receive light from other sources in the area.)
  • To show that two identical objects can cast different shadows.
  • To use a simple ray tracing diagram to predict the shadow of an object.

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