Glossary

atomic spectra

the electromagnetic emission from atoms and molecules

binding energy

also called the work function; the amount of energy necessary to eject an electron from a material

blackbody

an ideal radiator, which can radiate equally well at all wavelengths

blackbody radiation

the electromagnetic radiation from a blackbody

bremsstrahlung

German for braking radiation; produced when electrons are decelerated

characteristic x rays

x rays whose energy depends on the material they were produced in

Compton effect

the phenomenon whereby x rays scattered from materials have decreased energy

correspondence principle

in the classical limit (large, slow-moving objects), quantum mechanics becomes the same as classical physics

de Broglie wavelength

the wavelength possessed by a particle of matter, calculated by $\lambda =h/p$

gamma ray

also $\gamma$-ray; highest-energy photon in the EM spectrum

Heisenberg’s uncertainty principle

a fundamental limit to the precision with which pairs of quantities (momentum and position, and energy and time) can be measured

infrared radiation

photons with energies slightly less than red light

ionizing radiation

radiation that ionizes materials that absorb it

microwaves

photons with wavelengths on the order of a micron ($\text{μm}$)

particle-wave duality

the property of behaving like either a particle or a wave; the term for the phenomenon that all particles have wave characteristics

photoelectric effect

the phenomenon whereby some materials eject electrons when light is shined on them

photon

a quantum, or particle, of electromagnetic radiation

photon energy

the amount of energy a photon has; $E=\text{hf}$

photon momentum

the amount of momentum a photon has, calculated by $p=\frac{h}{\lambda }=\frac{E}{c}$

Planck’s constant

$h=6\text{.}\text{626}\times {\text{10}}^{\text{–34}}\text{J}\cdot \text{s}$

probability distribution

the overall spatial distribution of probabilities to find a particle at a given location

quantized

the fact that certain physical entities exist only with particular discrete values and not every conceivable value

quantum mechanics

the branch of physics that deals with small objects and with the quantization of various entities, especially energy

ultraviolet radiation

UV; ionizing photons slightly more energetic than violet light

uncertainty in energy

lack of precision or lack of knowledge of precise results in measurements of energy

uncertainty in momentum

lack of precision or lack of knowledge of precise results in measurements of momentum

uncertainty in position

lack of precision or lack of knowledge of precise results in measurements of position

uncertainty in time

lack of precision or lack of knowledge of precise results in measurements of time

visible light

the range of photon energies the human eye can detect

x ray

EM photon between $\gamma$-ray and UV in energy