Glossary

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scientific method - a systematic method of observation, experimentation, and analysis in order to construct an accurate representation of the world.

sclerotic - the tough white surface of the eyeball.

secondary colours - colours formed by mixing two primary colours.

secondary focus (F') - a focal point on the opposite side of a lens from the principal focus. Since light can pass from either direction or a lens may be flipped around, there are focal lengths on both sides of the lens.

shutter - a device on cameras that opens and closes quickly at variable speeds to let in the light. The shutter is normally closed and on high quality cameras can open and close from 1/1000 to 1 second.

significant digits - the number of digits that are valid for a measurement.

sonar - (sound navigation and ranging) equally spaced sound waves sent and reflected back. Sonar is used to determine sea depth, submarines and schools of fish.

sonic boom - an intense pressure or shock wave produced from an object traveling faster than the speed of sound. The sonic boom is usually heard as a sharp crack or cracks, like thunder.

specular reflection - parallel incident rays that are reflected parallel from a smooth surface (sometimes called regular reflection).

specific heat capacity - the quantity of heat (energy) needed to raise the temperature of unit of mass of a substance by a unit of temperature change.

spherical aberration - an optical defect in curved mirrors that result in reflected rays not all converging at a principal focus.

standing wave - reflected waves from the end of a medium interfering with incident waves so that specific points appear to be standing still.

subsonic - speed less than the speed of sound.

supersonic - speed greater than the speed of sound.

surface waves - a combination of transverse and longitudinal waves at the surface of water.

Suspensory ligaments - together with the ciliary muscles control the size of the pupil which lets in variable amounts of light.

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