Glossary

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eclipse - a shadow formed from a moon or planet blocking the light from the sun. A total eclipse is the umbra of a shadow while a partial eclipse would be the penumbra of a shadow.

electromagnetic spectrum - a continuum of electromagnetic waves or energies that include radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays.

electromagnetic waves - disturbances made up of electric and magnetic fields that do not require a medium for travel.

Eustachian tube - a tube connecting the mouth to the middle ear, allowing air pressure to be equal on both sides of the eardrum.

focal plane - the distance between the principal focus and the vertex.

filter - a transparent object that selectively absorbs and transmits light. A red filter absorbs all colours of light except red which is transmitted.

fovea - the concave centre of the retina that has the most concentrated area of rods and cones.

frequency - the number of oscillations or vibrations per second.

fundamental - the lowest frequency or pitch that will produce a standing wave in one segment.

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