Glossary

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radiation - the transfer of energy through space by electromagnetic waves.

radius of curvature - the distance from the center of curvature to the mirror.

rarefaction - the region between compressions in a longitudinal wave.

ray - a hypothetical line used to represent a single stream of light. Rays show the path of light but do not exist in nature.

real image - an image that can be focused or projected on a screen.

recomposition - the recombining of coloured light into white light.

rectilinear propagation - light travels in straight lines (sometimes just called linear propagation).

reflected ray - a portion of the incident ray that leaves or reflects a surface at the point of incidence.

refraction - the bending of light (or other waves) that takes place at a boundary between two different mediums. Refraction is due to a change in the speed of light as it passes from one medium to another.

resonant box - a box, sounding board, or instrument that amplifies the sound.

resonant length - specific lengths of an air column where the sound appears the loudest.

retina - the light sensitive region at the back of the eye that transmits the images you see to the brain.

reverberation - a echo following so closely to the original sound that the original sound appears to be just prolonged.

rods - structures located on the retina that are sensitive to dim light.

RSI value - resistance to heat loss value expressed in metric terms.

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