One of the effects of a substance or medium on light or other electromagnetic radiation passing through it, such as absorption, scattering, refraction, and polarization.

1. Also known as reflection property.

2. The property of an ellipse whereby rays of light emanating from one focus and reflected from a strip of polished metal at the ellipse come together at the other focus.

3. The property of a parabola whereby rays of light emanating from the focus and reflected from a strip of polished metal at the parabola are reflected parallel to the axis of the parabola, and likewise rays parallel to the axis of the parabola are reflected and brought together at the focus.

4. The property of a hyperbola whereby rays emanating from a focus and reflected from a strip of polished metal at the hyperbola appear to emanate from the other focus.