Chapter 2 Term

Question 1

Electromagnetic radiation

Answer 1

Another term for light, electromagnetic radiation transfers energy and information from one place to another.

Question 2

Visible light

Answer 2

The small range of the electromagnetic spectrum that human eyes perceive as light. The visible spectrum ranges from about 400 to 700 nm, corresponding to blue through red light.

Question 3

Radio

Answer 3

Region of the electromagnetic spectrum corresponding to radiation of the longest wavelengths.

Question 4

Infrared

Answer 4

Region of the electromagnetic spectrum just outside the visible range, corresponding to light of a slightly longer wavelength than red light.

Question 5

Ultraviolet

Answer 5

Region of the electromagnetic spectrum, just beyond the visible range, corresponding to wavelengths slightly shorter than the blue light.

Question 6

X-ray

Answer 6

Region of the electromagnetic spectrum corresponding to radiation of high frequency and short wavelength, far beyond the visible spectrum.

Question 7

Gamma Ray

Answer 7

Region of the electromagnetic spectrum, far beyond the visible spectrum, corresponding radiation of very high frequency and very short wavelength.

Question 8

Wave

Answer 8

A pattern that repeats itself cyclically in both time and space. Waves are characterized by the speed at which they move, their frequency, and their wavelength.

Question 9

Diffraction

Answer 9

The ability of waves to bend around corners. The diffraction of light establishes its wave nature.

Question 10

Interference

Answer 10

The ability of two or more waves to interact in such a way that they either reinforce or cancel each other.

Question 11

Electron

Answer 11

An elementary particle with a negative electric charge; one of the components of the atom.

Question 12

Proton

Answer 12

An elementary particle carrying a positive electric charge, a component of all atomic nuclei. The number of protons in the nucleus of an atom dictates what type of atom it is.

Question 13

Electric field

Answer 13

A field extending outward in all directions from a charged particle, such as a proton or an electron. The electric field determines the electric force exerted by the particle on all other charged particles in the universe; the strength of the electric field decreases with increasing distance from the charge according to an inverse-square law.

Question 14

Magnetic field

Answer 14

Field that accompanies any changing electric field and governs the influence of magnetized objects on one another.

Question 15

Electromagnetism

Answer 15

The union of electricity and magnetism, which do not exist as independent quantities but are in reality two aspects of a single physical phenomenon.

Question 16

Speed of light

Answer 16

The fastest possible speed, according to the current known laws of physics. Electromagnetic radiation exists in the form of waves or photons moving at the speed of light.

Question 17

Electromagnetic spectrum

Answer 17

The complete range of electromagnetic radiation, from radio waves to gamma rays, including the visible spectrum. All types of electromagnetic radiation are basically the same phenomenon, differing only by wavelength, and all move at the speed of light.

Question 18

Opacity

Answer 18

A quantity that measures a material’s ability to block electromagnetic radiation. Opacity is the opposite of transparency.

Question 19

Temperature

Answer 19

A measure of the amount of heat in an object, and an induction of the speed of the particles that comprise it.

Question 20

Intensity

Answer 20

A basic property of electromagnetic radiation that specifies the amount or strength of the radiation.

Question 21

Blackbody curve

Answer 21

The characteristic way in which the intensity of radiation emitted by a hot object depends on frequency. The frequency at which the emitted intensity is highest is an indication of the temperature of the radiating object. Also referred to as the Planck curve.

Question 22

Wien’s law

Answer 22

Relation between the wavelength at which a blackbody curve peaks and the temperature of the emitter. The peak wavelength is inversely proportional to the temperature, so the hotter the object, the bluer its radiation.

Question 23

Stefan’s law

Answer 23

Relation that gives the total energy emitted per square centimeter of its surface per second by an object of a given temperature. Stefan’s law shows that the energy emitted increases rapidly with an increase in temperature, proportional to the temperature raised to the fourth power.

Question 24

Spectroscope

Answer 24

Instrument used to view a light source so that it is split into its component colors.

Question 25

Continuous spectra

Answer 25

Spectra in which the radiation is distributed over all frequencies, not just a few specific frequency ranges. A prime example is the blackbody radiation emitted by a hot, dense body.

Question 26

Emission line

Answer 26

Bright line in a specific location of the spectrum of radiating material, corresponding to emission of light at a certain frequency. A heated gas in a glass container produces emission lines in its spectrum.

Question 27

Emission spectrum

Answer 27

The pattern of spectral emission lines produced by an element. Each element has its own unique emission spectrum.

Question 28

Absorption line

Answer 28

Dark line in an otherwise continuous bright spectrum, where light within one narrow frequency range has been removed.

Question 29

Spectroscopy

Answer 29

The study of the way in which atoms absorb and emit electromagnetic radiation. Spectroscopy allows astronomers to determine the chemical composition of stars.

Question 30

Kirchhoff's laws

Answer 30

Three rules governing the formation of different types of spectra.

Question 31

Atom

Answer 31

Building block of matter, composed of positively charged protons and neutral neutrons in the nucleus surrounded by negatively charged electrons.

Question 32

Nucleus

Answer 32

Dense, central region of an atom containing both protons and neutrons and orbited by one or more electrons. The solid region of ice and dust that composes the central region of the head of a comet. The dense central core of a galaxy.

Question 33

Bohr model

Answer 33

First theory of the hydrogen atom to explain the observed spectral lines. This model rests on three ideas: that there is a state of lowest energy for the electron, that there is a maximum energy beyond which the electron is no longer bound to the nucleus, and that within these two energies the electron can only exist in certain energy levels.

Question 34

Ground state

Answer 34

The lowest energy state that an electron can have within an atom

Question 35

Excited state

Answer 35

State of an atom when one of its electrons is in a higher energy orbital than the ground state. Atoms can become excited by absorbing a photon of a specific energy or by colliding with a nearby atom.

Question 36

Photon

Answer 36

Individual packet of electromagnetic energy that makes up electromagnetic radiation.

Question 37

Element

Answer 37

Matter made up of one particular atom. The number of protons in the nucleus of the atom determines which element it represents.

Question 38

Neutron

Answer 38

An elementary particle with roughly the same mass as a proton, but which is electrically neutral. Along with protons, neutrons form the nuclei of atoms.

Question 39

Doppler effect

Answer 39

Any motion-induced change in the observed wavelength (or frequency) of a wave.