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Chemistry and physics lessons
atom physics lesson

Optics

Free online optic lesson for elementary school,  middle school and high school.
chemistry high school
 




















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Shadows, lunar eclipses and phases of the moon

Formation of shadows

 
1) What is a shadow ?

When an opaque object is lighted, some areas, located behind the object, don't receive light and form the shadow of the object.
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2) Core shadow and cast shadow

When an opaque object is lighted, two kind of shadows can be distinguished:
- The core shadow is the part of the object that doesn't receive light. This part is at the opposite side of the light source.
- The cast shadow consist of
- The core shadow is located on a surface behind the object (screen, wall, floor etc.) that doesn't receive light. This shadow has a shape that reproduces contours of the lighted object.
As for the space between core shadow and cast shadow, it can be called " cone shadow ".

Example: a sphere lighted by a tiny light source
Cast shadow and core shadow of a lighted sphere

 


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