ALGEBRA 1 Version 2009
Revised and highly enlarged.
ALGEBRA 2
ALGEBRA 3
ALGEBRA 4
GEOMETRY 1
ELECTRICITY 1
ELECTRICITY 2
ELECTRICITY 1&2
OPTICS 1
OPTICS 2
MECHANICS 3
 
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 OPTICS 1
 
  free extract of chapter : 10

     10. Light, umbra and penumbra.
            1. Rectilinear propagation of light.
            6. Observing the Umbra and penumbra of a ball lit by a light source.

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