Astronomy Exam 2

Front 1

speed

Back 1

the rate at which an object moves. Its units are distance divided by time

Front 2

velocity

Back 2

the combination of speed and direction of motion; it can be stated as a speed in a particular direction

Front 3

acceleration

Back 3

the rate at which an object's velocity changes

Front 4

acceleration due to gravity

Back 4

the acceleration of a falling object. on Earth, the acceleration due to gravity is 9.8 m/s^2

Front 5

momentum

Back 5

the product of an object's mass and velocity

Front 6

force

Back 6

anything that can cause a change in momentum

Front 7

net force

Back 7

the overall force to which an object responds; the net force is equal to the rate of change in the object's momentum, or equivalently to the object's mass x acceleration

Front 8

angular momentum

Back 8

momentum attributable to rotation or revolution. the angular momentum of an object moving in a circle of radius r is the product m x v r

Front 9

mass

Back 9

a measure of the amount of matter in an object

Front 10

weight

Back 10

the net force that an object applies to its surroundings; in the case of a stationary body on the surface of Earth, it equals mass x acceleration of gravity

Front 11

rotational angular momentum

Back 11

angular momentum due to the Earth's rotation

Front 12

orbital angular momentum

Back 12

angular momentum due to Earth's orbit around Sun

Front 13

torque

Back 13

a twisting force that can cause a change in an object's angular momentum

Front 14

free-fall

Back 14

the condition in which an object is falling without resistance; objects are weightless when in free-fall

Front 15

weightless

Back 15

a weight of zero, as occurs during free-fall

Front 16

Newton's 1st Law

Back 16

an object moves at a constant velocity if there is no net force acting upon it

Front 17

Newton's 2nd Law

Back 17

F=ma

force = rate of change in momentum

Front 18

Newton's 3rd Law

Back 18

For any force, there is always an equal and opposite reaction force

Front 19

conservation of momentum

Back 19

the principle that, in the absence of a net force, the total momentum of a system remains constant

Front 20

conservation of angular momentum

Back 20

the principle in that, in the absence of a net torque, the total angular momentum of a system remains constant

Front 21

conservation of energy

Back 21

the principle that energy can be neither created nor destroyed, but can only change from one form to another

Front 22

kinetic energy

Back 22

- energy of motion

- 1/2 mv^2

Front 23

radiative energy

Back 23

energy carried by light; the energy of a photon is Planck's constant times its frequency

- E = hf

Front 24

potential energy

Back 24

energy stored for later conversion into kinetic energy; includes gravitational potential energy, electric potential energy, and chemical potential energy

Front 25

joule

Back 25

the international unit of energy, equivalent to about 1/4000 of a calorie

Front 26

thermal energy

Back 26

- the collective kinetic energy, as measured by temperature, of the many individual particles moving with a substance

- total kinetic energy

Front 27

temperature

Back 27

- a measure of the avg. kinetic energy of particles in a substance

- average kinetic energy

Front 28

Kelvin

Back 28

the most commonly used temperature scale in science, defined such that absolute zero is 0 K and water freezes at 273.15 K

Front 29

gravitational potential energy (GPE)

Back 29

energy that an object has by virtue of its position in a gravitational field; an object has more gravitational potential energy when it has a greater distance that it can potentially fall

Front 30

mass-energy

Back 30

the potential energy of mass, which has an amount E = mc^2

Front 31

orbital energy

Back 31

the sum of an orbiting object's kinetic and GPE's

Front 32

gravitational encounter

Back 32

an encounter in which two or more objects pass near enough so that each can feel the effects of the other's gravity and they can therefore exchange energy

Front 33

escape velocity

Back 33

the speed necessary for an object to completely escape the gravity of a large body such as a moon, planet, or star

Front 34

tidal force

Back 34

a force that occurs when the gravity pulling on one side of an object is larger than that on the other side, causing the object to stretch

Front 35

tidal friction

Back 35

friction within an object that is caused by a tidal force

Front 36

power

Back 36

the rate of energy usage, usually measured in watts

Front 37

watts

Back 37

the standard unit of power, 1 joule/s

Front 38

diffraction grating

Back 38

a finely etched surface that can split light into a spectrum

Front 39

emission

Back 39

the process by which matter emits energy in the form of light

Front 40

absorption

Back 40

the process by which matter absorbs radiative energy

Front 41

transmission

Back 41

the process in which light passes through matter without being absorbed

Front 42

reflection/scattering

Back 42

the process by which matter changes the direction of light

Front 43

wavelength

Back 43

the distance between adjacent peaks of a wave

Front 44

frequency

Back 44

the rate at which peaks of a wave pass by a point, measured in units of 1/d, often cycles per second or hertz

Front 45

cycles per second

Back 45

units of frequency for a wave; describes the number of peaks or troughs of a wave that pass by a given point each second

Front 46

hertz

Back 46

standard unit of frequency for light waves, 1/s

Front 47

field

Back 47

an abstract concept used to describe how a particle would interact with a force

Front 48

electromagnetic wave

Back 48

a synonym for light, which consists of waves of electric and magnetic fields

Front 49

speed of light

Back 49

300,000 km/s

Front 50

photons

Back 50

an individual particle of light, characterized by a wavelength and a frequency

Front 51

electromagnetic spectrum

Back 51

the complete spectrum of light

Front 52

electromagnetic radiation

Back 52

another name for light of all types on the spectrum

Front 53

visible light

Back 53

the light our eyes can see ranging from 400 to 700 nm

Front 54

microwaves

Back 54

generally considered a subset of radio waves

Front 55

atoms

Back 55

a nucleus made from protons and neutrons, surrounded by a cloud of electrons

Front 56

element

Back 56

a substance made from individual atoms of a particular atomic number

Front 57

protons

Back 57

particles found in atomic nuclei with positive charge, made of three quarks

Front 58

neutrons

Back 58

no electrical charge, built from three quarks

Front 59

electrons

Back 59

fundamental particles with negative charge, distribution of electrons gives atoms size

Front 60

nucelus

Back 60

compact center made from protons and neutrons

Front 61

electrical charge

Back 61

a property of matter that is described by its amount and as either positive or negative; more technically, a measure of how a particle responds to electromagnetic force

Front 62

atomic number

Back 62

the number of protons in an atom

Front 63

atomic mass number

Back 63

combined number of protons and neutrons in an atom

Front 64

isotopes

Back 64

forms of an element that have the same number of protons but different numbers of neutrons

Front 65

molecules

Back 65

combinations of two or more atoms held together by chemical bonds

Front 66

phase

Back 66

state determined by the way in which atoms or molecules are held together

Front 67

solid

Back 67

atoms or molecules are held rigidly in place

Front 68

liquid

Back 68

atoms or molecules are held together but move freely

Front 69

gas

Back 69

atoms or molecules can move essentially independent of one another

Front 70

chemical bond

Back 70

interactions between electrons that hold atoms in a molecule together

Front 71

sublimation

Back 71

atoms or molecules escape into the gas phase from a solid

Front 72

evaporation

Back 72

from liquid to gas phase

Front 73

molecular dissociation

Back 73

a molecule splits into its component atoms

Front 74

ions

Back 74

atoms with a positive or negative charge

Front 75

ionization

Back 75

the process of stripping an electron from an atom

Front 76

plasma

Back 76

gas consisting of ions and electrons

Front 77

pressure

Back 77

force per unit area pushing on an object

Front 78

energy levels

Back 78

possible energies of an electron in an atom

Front 79

energy level transitions

Back 79

an electron can rise from a lower level to a higher one or fall from high to low

Front 80

spectroscopy

Back 80

process of obtaining spectra from astronomical objects

Front 81

intensity

Back 81

measure of the amount of energy coming from light of a specific wavelength

Front 82

continuous spectrum

Back 82

a spectrum that spans a broad range of wavelengths without interruption by emission or absorption lines

Front 83

emission lines

Back 83

what indicate different lights on a spectrum

Front 84

emission line spectrum

Back 84

a spectrum that contains emission lines

Front 85

absorption lines

Back 85

what appears when certain wavelengths of light are captured

Front 86

absorption line spectrum

Back 86

a spectrum that contains absorption lines

Front 87

molecular bands

Back 87

tightly bunched lines in an object's spectrum that are produced by molecules

Front 88

thermal radiation

Back 88

spectrum of radiation produced by an opaque object that depends only on the object's temperature; sometimes called blackbody radiaton

Front 89

Two Laws of Thermal Radiation

Back 89

1. each square meter of a hotter object emits more light at all wavelengths

2. Wien's law - hotter objects emit photons with a higher average energy

Front 90

Doppler Effect

Back 90

the effect that shifts the wavelengths of spectral features in objects that are moving toward or away from the observer

Front 91

blueshift

Back 91

shorter wavelengths from Doppler Effect, object moving toward observer

Front 92

redshift

Back 92

longer wavelengths from Doppler Effect, object moving away from observer

Front 93

focal point (focus)

Back 93

the point at which rays of light that were initially parallel converse (such as those from a distant star)

Front 94

focal plane

Back 94

the place where an image created by a lens or mirror is in focus

Front 95

detector

Back 95

the place on a camera where light is recorded into a permanent image

Front 96

exposure time

Back 96

the amount of time during which light is collected to make a single image

Front 97

pixels

Back 97

and individual "picture element" on a CCD (Charge Coupled Device - type of electronic light detector)

Front 98

light-collecting area

Back 98

the area of the primary mirror or lens that collects light in a telescope

Front 99

angular resolution

Back 99

the smallest angular separation that two pointlike objects can have an sill be seen as distinct points of light (rather than as a single point of light)

Front 100

diffraction limit

Back 100

the angular resolution that a telescope could achieve if it were limited only by the interference of light waves; it is smaller for larger telescopes

Front 101

refracting telescope

Back 101

a telescope that uses lenses to focus light

Front 102

reflecting telescope

Back 102

a telescope that uses mirrors to focus light

Front 103

spectrographs

Back 103

an instrument used to record spectra

Front 104

light curves

Back 104

a graph of an object's intensity against time

Front 105

light pollution

Back 105

human-made light that hinders astronomical observations

Front 106

turbulence

Back 106

rapid and random motion

Front 107

adaptive optics

Back 107

a technique in which telescope mirrors flex rapidly to compensate for the bending of starlight caused by atmosphere turbulence

Front 108

grazing incidence mirrors

Back 108

reflections in which light grazes a mirror surface and is deflected at a small angle; commonly used to focus high-energy ultraviolet light and x rays

Front 109

interferometry

Back 109

a telescopic technique in which two or more telescopes are used in tandem to produce much better angular resolution than the telescopes could achieve individually

Front 110

image

Back 110

a picture of an object made by focusing light

Front 111

inverse square law

Back 111

a law stating that the intensity of an effect such as illumination or gravitational force changes in inverse proportion to the square of the distance from the source.

Front 112

universal law of gravitation

Front 113

unbound orbit

Back 113

hyperbola, parabola, paths that bring an object close to another object just once

Front 114

bound orbit

Back 114

ellipse, orbit in which an object goes around another object over and over again

Front 115

center of mass

Back 115

the point at which two objects would balance if they were somehow connected

Front 116

Newton's Version of Kepler's Third Law

Back 116

objects' characteristics tell us the masses of distant objects