Glossary

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nodes - points in a standing wave where the positive and negative pulses cancel each other resulting in areas of rest (no movement).

nonluminous body - a body that reflects light (eg. the moon).

normal - a construction line drawn perpendicular (90°) to the surface at the point of incidence.

objective lens - the lens closest to the object or specimen in a compound microscope, astronomical or terrestrial telescope.

opaque - an object or material that does not allow light to pass through.

open air column - a column of air inside a pipe or box where both ends are open.

optical centre (O) - the geometric centre of a lens.

optic nerve - a bundle of nerves that transmits the images from the retina to the brain.

oscilloscope - an instrument that converts sound waves into patterns of transverse waves that are projected on a monitor.

ossicles (hammer anvil & stirrup) - the tiny bones of the middle ear that are connected to the eardrum. These bones pass the vibrations from the eardrum to the cochlea and amplify all frequencies by a factor of 3.

overtones - higher resonant frequencies produced above a fundamental. Different combinations of overtones in voices or musical instruments allows the sounds to be distinguishable.

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