Astronomy Unit 1

Question 1

a series or pattern of dark lines superimposed on a continuous spectrum

Answer 1

absorption spectrum

Question 2

an idealized object that absorbs all electromagnetic energy that falls onto it

Answer 2

blackbody

Question 3

a spectrum of light composed of radiation of a continuous range of wavelengths or
colors, rather than only certain discrete wavelengths

Answer 3

continuous spectrum

Question 4

separation of different wavelengths of white light through refraction of different amounts

Answer 4

dispersion

Question 5

the apparent change in wavelength or frequency of the radiation from a source due to its
relative motion away from or toward the observer

Answer 5

Doppler effect

Question 6

radiation consisting of waves propagated through regularly varying electric and
magnetic fields and traveling at the speed of light

Answer 6

electromagnetic radiation

Question 7

the whole array or family of electromagnetic waves, from radio to gamma rays

Answer 7

electromagnetic spectrum

Question 8

a series or pattern of bright lines superimposed on a continuous spectrum

Answer 8

emission spectrum

Question 9

the amount of energy passing through a unit area (for example, 1 square meter) per second; the
units of flux are watts per square meter

Answer 9

energy flux

Question 10

a particular level, or amount, of energy possessed by an atom or ion above the energy it
possesses in its least energetic state; also used to refer to the states of energy an electron can have in an atom

Answer 10

energy level

Question 11

the process of giving an atom or an ion an amount of energy greater than it has in its lowest energy
(ground) state

Answer 11

excitation

Question 12

he number of waves that cross a given point per unit time (in radiation)

Answer 12

frequency

Question 13

photons (of electromagnetic radiation) of energy with wavelengths no longer than 0.01
nanometer; the most energetic form of electromagnetic radiation

Answer 13

gamma rays

Question 14

he lowest energy state of an atom

Answer 14

ground state

Question 15

electromagnetic radiation of wavelength 103–106 nanometers; longer than the longest (red)
wavelengths that can be perceived by the eye, but shorter than radio wavelength

Answer 15

infrared

Question 16

(for light) the amount of energy (light) flowing through a given area in a given time
decreases in proportion to the square of the distance from the source of energy or light

Answer 16

inverse square law

Question 17

an atom that has become electrically charged by the addition or loss of one or more electrons

Answer 17

ion

Question 18

the process by which an atom gains or loses electrons

Answer 18

ionization

Question 19

any of two or more forms of the same element whose atoms have the same number of protons but different numbers of neutrons

Answer 19

isotope

Question 20

electromagnetic radiation of wavelengths from 1 millimeter to 1 meter; longer than infrared but
shorter than radio waves.

Answer 20

microwave

Question 21

the massive part of an atom, composed mostly of protons and neutrons, and about
which the electrons revolve

Answer 21

nucleus

Question 22

a discrete unit (or “packet”) of electromagnetic energy

Answer 22

photon

Question 23

motion toward or away from the observer; the component of relative velocity that lies in the
line of sight

Answer 23

radical velocity

Question 24

all electromagnetic waves longer than microwaves, including radar waves and AM radio waves

Answer 24

radio waves

Question 25

an instrument for obtaining a spectrum; in astronomy, usually attached to a telescope to record the spectrum of a star, galaxy, or other astronomical object

Answer 25

spectrometer

Question 26

a formula from which the rate at which a blackbody radiates energy can be computed;
the total rate of energy emission from a unit area of a blackbody is proportional to the fourth power of itsnabsolute temperature: F = σT4

Answer 26

Stefan-Boltzmann law

Question 27

electromagnetic radiation of wavelengths 10 to 400 nanometers; shorter than the shortest visible
wavelengths

Answer 27

ultraviolet

Question 28

electromagnetic radiation with wavelengths of roughly 400–700 nanometers; visible to the human
eye

Answer 28

visible light

Question 29

the distance from crest to crest or trough to trough in a wave

Answer 29

wavelength

Question 30

formula that relates the temperature of a blackbody to the wavelength at which it emits the
greatest intensity of radiadion

Answer 30

Wien’s law

Question 31

electromagnetic radiation with wavelengths between 0.01 nanometer and 20 nanometers;
intermediate between those of ultraviolet radiation and gamma rays

Answer 31

x-rays