6A01.XX - SPEED OF LIGHT
6A02.XX - STRAIGHT LINE PROPAGATION OF
LIGHT
6A10.XX - REFLECTION FROM FLAT
SURFACES
6A20.XX - REFLECTION FROM CURVED
SURFACES
6A40.XX - REFRACTIVE INDEX
6A42.XX - REFRACTION AT FLAT
SURFACES
6A44.XX - TOTAL INTERNAL
REFLECTION
6A46.XX - RAINBOWS
6A60.XX - THIN LENSES
6A61.XX - PINHOLE
6A65.XX - THICK LENS
6A70.XX - OPTICAL INSTRUMENTS