Astronomy Chapter 4 Vocab

Front 1

absorption

Back 1

The process in which light or other electromagnetic radiation gives up its energy to an atom or molecule. For example, ozone in our atmosphere absorbs ultraviolet radiation.

Front 2

absorption-line spectrum

Back 2

A spectrum showing dark lines at some narrow color regions (wavelengths). The lines are formed by atoms absorbing light, which lifts their electrons to higher orbits.

Front 3

atmospheric window

Back 3

A wavelength band in which our atmosphere absorbs little radiation. For example, on Earth the visible window ranges from about 300 to 700 nanometers, allowing the light we can see with our eyes to pass through the atmosphere.

Front 4

blackbody

Back 4

An object that is an ideal radiator when hot and a perfect absorber when cool. It absorbs all radiation that falls upon it, reflecting no light; hence, it appears black. Stars are approximately blackbodies. The radiation emitted by blackbodies obeys Wien's law and the Stefan-Boltzmann law.

Front 5

conservation of energy

Back 5

A principle of physics stating that the energy is never created or destroyed, although it may change its form. For example, energy of motion may change into energy of heat.

Front 6

continuous spectrum

Back 6

A spectrum with neither dark absorption nor bright emission lines. The intensity of the radiation in such a spectrum changes smoothly from one wavelength to the next.

Front 7

Doppler shift

Back 7

The change in the observed wavelength of radiation caused by the motion of the emitting body or the observer. The shift is an increase in the wavelength if the source and observer move apart and a decrease in the wavelength if the source and observer approach.

Front 8

electromagnetic radiation

Back 8

A general term for any kind of electromagnetic wave.

Front 9

electromagnetic spectrum

Back 9

The assemblage of all wavelengths of electromagnetic radiation. The spectrum includes the following wavelengths, from long to short: radio, microwave, infrared, visible light, ultraviolet, x-rays, and gamma rays.

Front 10

electromagnetic wave

Back 10

A wave consisting of alternating electric and magnetic energy. Ordinary visible light is an electromagnetic wave, and the wavelength determines the light's color.

Front 11

element

Back 11

A fundamental substance, such as hydrogen, carbon, or oxygen, that cannot be broken down into a simpler chemical substance. Approximately 100 elements occur in nature.

Front 12

emission

Back 12

The production of light, or more generally, electromagnetic radiation by an atom or other object.

Front 13

emission-line spectrum

Back 13

A spectrum consisting of bright lines at a certain wavelengths separated by dark regions in which there is no light.

Front 14

energy level

Back 14

Any of the numerous orbitals that an electron can occupy in an atom or molecule, roughly corresponding to an electron orbit.

Front 15

excited

Back 15

The condition in which the electrons of an atom are not in their lowest energy level (orbit).

Front 16

frequency

Back 16

The number of times per second that a wave vibrates.

Front 17

infrared

Back 17

A wavelength of electromagnetic radiation longer than visible light but shorter than radio waves. We cannot see these waves with our eyes, but we can feel many of them as heat. The infrared wavelength region runs from about 700 nm to 1mm.

Front 18

light

Back 18

Electromagnetic energy.

Front 19

nanometer

Back 19

A unit of length equal to 1 billionth of a meter and abbreviated nm. Wavelengths of visible light are several hundred nanometers. The diameter of a hydrogen atom is roughly 0.1 nm.

Front 20

orbital

Back 20

A description of an electron's possible location in an atom as it "orbits" the nucleus. At these tiny scales, the electron's position can be described only in terms of probabilities, due to the wave nature of matter.

Front 21

photon

Back 21

A particle of visible light or other electromagnetic radiation.

Front 22

quantized

Back 22

The property of a system that allows it to have only discrete values.

Front 23

spectroscopy

Back 23

The study and analysis of spectra.

Front 24

ultraviolet

Back 24

A portion of the electromagnetic spectrum with wavelengths shorter than those of visible light but longer than those of x-rays. By convention, the ultraviolet region extends from about 10 nm to 400 nm.

Front 25

visible spectrum

Back 25

The part of the electromagnetic spectrum that we can see with our eyes. It consists of familiar colors violet, blue, green, yellow, orange, and red, extending from about 400 nm to 700 nm.

Front 26

wavelength

Back 26

The distance between wave crests, it determines the color of visible light.

Front 27

wave-particle duality

Back 27

The theory that electromagnetic radiation may be treated as either a particle (photon) or an electromagnetic wave.

Front 28

white light

Back 28

Visible light exhibiting no color of its own but composed of a mix of all colors. Sunlight and many artificial light sources are "white."

Front 29

Wien's law

Back 29

A relation between a body's temperature and the wavelength of which it emits radiation most intensely. Hotter bodies radiate more intensely at shorter wavelengths.