Chemistry » Electronic Structure of Atoms » Electromagnetic Energy

Glossary of Words

The following words are the keywords that have been introduced in the past few lessons. Understanding what each means and represents are crucial to grasping further lessons in this tutorial.



extent of the displacement caused by a wave (for sinusoidal waves, it is one-half the difference from the peak height to the trough depth, and the intensity is proportional to the square of the amplitude)


idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation

Continuous spectrum

electromagnetic radiation given off in an unbroken series of wavelengths (e.g., white light from the sun)

Electromagnetic radiation

energy transmitted by waves that have an electric-field component and a magnetic-field component

Electromagnetic spectrum

range of energies that electromagnetic radiation can comprise, including radio, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays; since electromagnetic radiation energy is proportional to the frequency and inversely proportional to the wavelength, the spectrum can also be specified by ranges of frequencies or wavelengths

Frequency (ν)

number of wave cycles (peaks or troughs) that pass a specified point in space per unit time

Hertz (Hz)

the unit of frequency, which is the number of cycles per second, s−1


property of wave-propagated energy related to the amplitude of the wave, such as brightness of light or loudness of sound

Interference pattern

pattern typically consisting of alternating bright and dark fringes; it results from constructive and destructive interference of waves

Line spectrum

electromagnetic radiation emitted at discrete wavelengths by a specific atom (or atoms) in an excited state


any point of a standing wave with zero amplitude


smallest possible packet of electromagnetic radiation, a particle of light


occurring only in specific discrete values, not continuous

Standing wave

(also, stationary wave) localized wave phenomenon characterized by discrete wavelengths determined by the boundary conditions used to generate the waves; standing waves are inherently quantized


oscillation that can transport energy from one point to another in space

Wavelength (λ)

distance between two consecutive peaks or troughs in a wave

Wave-particle duality

term used to describe the fact that elementary particles including matter exhibit properties of both particles (including localized position, momentum) and waves (including non-localization, wavelength, frequency)

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