Infrared Spectroscopy


absorption spectroscopy

measurement of the amount of light absorbed by a compound as a function of the wavelength of light


height of a wave, measured as the distance from the point of equilibrium to a crest or trough

electromagnetic radiation

wave of energy produced by the movement of photons through space

electromagnetic spectrum

entire range of electromagnetic waves, defined by their energy, wavelengths, and frequencies


number of oscillations of a wave that occur in a given period of time, usually a second, measured in hertz (Hz)

functional group

group of atoms with specific physical, chemical, and reactivity properties

infrared light

region of the electromagnetic spectrum that corresponds to frequencies from just below the visible light frequencies to just above the highest microwave and radar frequencies

infrared spectrometer

instrument that measures the frequencies of infrared light absorbed by a compound

infrared spectroscopy

method that observes the vibrations of bonds and provides evidence of the functional groups present

infrared spectrum

graph of the energy absorbed or transmitted by a molecule as a function of the frequency or wavelength of light

photoelectric effect

emission of electrons when light strikes a material


fundamental particle that has a fixed amount of energy stored as electromagnetic radiation


study of how light interacts with matter

ultraviolet spectroscopy

method that observes electronic transitions and provides information on the electronic bonding in the sample


periodic oscillation of energy or matter

wave number

number of wavelengths of the wave in a centimeter; or the reciprocal of the wavelength (in centimeters)

wave-particle duality

concept that light has properties of both particles and waves


distance between two identical parts of a wave