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This document discusses properties of light and vision. It defines luminous objects as those that produce their own light, like the sun and fire, and non-luminous objects as those that are visible through reflected light, like tables and planets. It discusses the rectilinear propagation of light in a straight line and the reflection of light. Key terms covered include transparent, translucent, opaque, incident rays, and reflected rays. Students are assigned homework questions to classify materials as luminous or non-luminous and as transparent, translucent or opaque, and to answer questions about reflections and looking at the sun.