http://www.ck12.org Chapter 26. Glossary
26.18 R
radar
radio detection and ranging; use of reflected radio waves to track the position of objects
radiation
general term for the charged particles and energy emitted by the nucleus of a radioisotope, or for energy
emitted when charged particles accelerate
radioactive dating
method of determining the age of fossils or rocks that is based on the rate of decay of radioisotopes
radioactive decay
process in which unstable nuclei of radioisotopes become stable by emitting charge particles and energy and
becoming other elements
radioactivity
ability of an atom to emit charged particles and energy from the nucleus
radioisotope
radioactive isotope, or isotope that emits radiation from its nucleus
radio wave
any wave in the electromagnetic spectrum that has a wavelength longer than infrared light
range
total spread of values in a set of measurements that is calculated by subtracting the smallest value from the
largest value
reactant
substance that starts a chemical reaction
reaction rate
speed at which a chemical reaction occurs
reactivity
ability of matter to combine chemically with other substances
reflection
bouncing back of waves from a barrier they cannot pass through
refraction
bending of waves as they enter a new medium at an angle and change speed
refrigerant
substance with a low boiling point that is used to transfer thermal energy in a cooling system such as a
refrigerator
renewable resource
natural resource that can be replaced in a relatively short period of time or is virtually limitless in supply
replacement reaction
chemical reaction in which ions switch places in one compound (single replacement) or in two compounds
(double replacement)
replication
getting the same results when an investigation is repeated
resistance
opposition to the flow of electric charges that occurs when electric current travels through matter
resonance
vibration of an object in response to sound waves of a certain frequency
responding variable
factor in an experiment that is expected to change, or respond, when the manipulated variable changes; also