Glossary

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temperature - the average of potential and kinetic energies in a substance.

terrestrial telescope - a telescope for viewing objects on Earth. Terrestrial telescopes use 3 lenses and the image appears upright.

thermal energy - the total or sum of the potential and kinetic energies in a substance.

thermal expansion - the expanding of a substance due to an increase in temperature and the contracting of a substance due to a decrease in temperature.

thermal resistance - the ability of a given thickness of a substance to prevent heat transfer.

thermodynamics - the branch of physics that deals with the relationship between heat and other forms of energy.

threshold of hearing - the lowest intensity of sound that can be heard. Although threshold of hearing is defined as 0 dB, it varies with different frequencies.

total internal reflection - results when the angle of incidence is greater than the critical angle of a medium. Light does not passes through and refract, rather it simply reflects off the boundary surface.

translucent - objects that allow some light to pass through but diffuse or scatter in the process. A clear image is not visible through this object.

transparent - objects that allow light to pass through them so that a clear image is visible.

transverse waves - waves such as water or slinky waves where the particles in the medium move or vibrate perpendicular to the direction of the wave.

trough - the bottom of a transverse wave.

tympanic membrane (eardrum)- a tough, tightly stretched membrane less than 0.1 mm thick that vibrates at the same frequency as the source. The eardrum passes these vibrations on to the middle ear.

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