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AstronomyAstronomy

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What is Astronomy?What is Astronomy?

Astronomy is the study Astronomy is the study of objects in the of objects in the UniverseUniverse

Astronomers study the Astronomers study the Universe using Universe using telescopes, satellites, telescopes, satellites, probes, as well as probes, as well as manned and unmanned manned and unmanned space flights space flights

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What’s in the Universe?What’s in the Universe?

GalaxiesGalaxiesStarsStarsSolar systemsSolar systemsPlanets and their moonsPlanets and their moonsAsteroidsAsteroidsCometsCometsNebulasNebulas

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The Origin of the UniverseThe Origin of the Universe

Astronomers believe that Astronomers believe that about 15 to 20 billion about 15 to 20 billion years ago all the matter years ago all the matter and energy in the and energy in the Universe were Universe were concentrated into one concentrated into one point called a singularity point called a singularity

Tremendous amounts of Tremendous amounts of heat and pressure made heat and pressure made this point so unstable that this point so unstable that it explodedit exploded

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The Big Bang TheoryThe Big Bang Theory

The The Big Bang TheoryBig Bang Theory states that the states that the Universe began to expand after an Universe began to expand after an enormous explosion of concentrated enormous explosion of concentrated matter and energy matter and energy

After the initial explosion, gravity pulled the After the initial explosion, gravity pulled the matter into huge clumps which formed the matter into huge clumps which formed the galaxiesgalaxies

Even as the galaxies were forming, Even as the galaxies were forming, everything continued to race outward, everything continued to race outward, expanding the Universeexpanding the Universe

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The Fate of the UniverseThe Fate of the Universe

Background radiation, left over from the Background radiation, left over from the Big Bang, has led astronomers to two Big Bang, has led astronomers to two possible fates for the Universe possible fates for the Universe

Open Universe-Open Universe- A universe that would A universe that would continue to expandcontinue to expand

Closed Universe-Closed Universe- A universe that would A universe that would expand then collapse back in on itselfexpand then collapse back in on itself

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An Open UniverseAn Open Universe

A possible future where the galaxies A possible future where the galaxies continue racing outward, expanding the continue racing outward, expanding the Universe Universe

Stars would eventually die off as the last of Stars would eventually die off as the last of their energy was releasedtheir energy was released

After billions of years there would be After billions of years there would be nothing left of the Universenothing left of the Universe

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A Closed UniverseA Closed Universe

The expansion of the Universe would The expansion of the Universe would eventually come to a halt eventually come to a halt

Gravity would begin to pull the galaxies Gravity would begin to pull the galaxies back toward the center of the Universeback toward the center of the Universe

After many billions of years, all the matter After many billions of years, all the matter and energy in the Universe would again be and energy in the Universe would again be concentrated in a single pointconcentrated in a single point

A new “Big Bang” could occur every 80 to A new “Big Bang” could occur every 80 to 100 billion years100 billion years

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Galaxies Galaxies

A galaxy is a large A galaxy is a large system of stars and system of stars and other cosmic bodiesother cosmic bodies

Galaxies are the major Galaxies are the major features of the Universefeatures of the Universe

There may be more There may be more than 100 billion major than 100 billion major galaxies galaxies

There are three main There are three main types of galaxiestypes of galaxies

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Spiral GalaxiesSpiral Galaxies

Shaped like pinwheelsShaped like pinwheelsMillions of stars make up a bright nucleus Millions of stars make up a bright nucleus Usually have two spiral arms protruding Usually have two spiral arms protruding

out from opposite sides of the nucleusout from opposite sides of the nucleusThe arms contain millions of stars along The arms contain millions of stars along

with clouds of dust and gas with clouds of dust and gas

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Elliptical GalaxiesElliptical GalaxiesVary in shape from nearly spherical to Vary in shape from nearly spherical to

flattened disksflattened disksMost of the stars are close to the centerMost of the stars are close to the centerHave no armsHave no armsContain very little gas or dustContain very little gas or dustStars are generally older than those in the Stars are generally older than those in the

other galaxiesother galaxies

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Irregular GalaxiesIrregular Galaxies

Have no definite shapeHave no definite shapeStars are spread unevenlyStars are spread unevenlySmaller, fainter, and less Smaller, fainter, and less

common than other galaxiescommon than other galaxies

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The Solar SystemThe Solar System

A huge rotating system consisting of the A huge rotating system consisting of the Sun, eight planets and their satellites, Sun, eight planets and their satellites, dwarf planets, asteroids, comets, and dwarf planets, asteroids, comets, and meteorsmeteors

Astronomers use the Astronomers use the Nebular TheoryNebular Theory to to explain the formation of our solar explain the formation of our solar systemsystem

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The Nebular TheoryThe Nebular Theory According to the nebular theory, our solar According to the nebular theory, our solar

system began as a great cloud of dust and system began as a great cloud of dust and frozen gasesfrozen gases

About 5 billion years ago this rotating cloud About 5 billion years ago this rotating cloud began to contractbegan to contract

As the nebula contracted, it spun faster and As the nebula contracted, it spun faster and flattened itself into a disk shaped cloudflattened itself into a disk shaped cloud

Compression of the matter in the center of the Compression of the matter in the center of the cloud ignited the hydrogen located there, cloud ignited the hydrogen located there, forming the Sunforming the Sun

The remaining material orbiting the Sun The remaining material orbiting the Sun collected into a number of huge whirlpools that collected into a number of huge whirlpools that eventually became the planets and their moonseventually became the planets and their moons

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The Planets in the Solar SystemThe Planets in the Solar System

The eight planets in the The eight planets in the Solar System, named in Solar System, named in order of increasing order of increasing distance from the Sun distance from the Sun are: Mercury, Venus, are: Mercury, Venus, Earth, Mars, Jupiter, Earth, Mars, Jupiter, Saturn, Uranus, & Saturn, Uranus, & NeptuneNeptune

Astronomers use Astronomers use

various criteria to various criteria to

group the planetsgroup the planets

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Inner vs. Outer PlanetsInner vs. Outer Planets

The asteroid belt is used as a dividing line The asteroid belt is used as a dividing line to separate the planets into two groupsto separate the planets into two groups

The inner planets-The inner planets- Mercury, Venus, Earth Mercury, Venus, Earth and Mars (located between the Sun & the and Mars (located between the Sun & the asteroid belt)asteroid belt)

The outer planets-The outer planets- Jupiter, Saturn, Jupiter, Saturn, Uranus, and Neptune (located beyond the Uranus, and Neptune (located beyond the asteroid belt)asteroid belt)

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Terrestrial vs. Jovian PlanetsTerrestrial vs. Jovian PlanetsTerrestrial Planets-Terrestrial Planets- Planets that are Planets that are

Earth-like, in that they have a solid, Earth-like, in that they have a solid, rocky surface rocky surface

Mercury, Venus, Earth, and MarsMercury, Venus, Earth, and Mars

Jovian Planets-Jovian Planets- Planets that are Planets that are Jupiter-like, in that they are primarily Jupiter-like, in that they are primarily made of gas made of gas

Jupiter, Saturn, Uranus, and NeptuneJupiter, Saturn, Uranus, and Neptune

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Rotation vs. RevolutionRotation vs. Revolution

Rotation-Rotation- The time it takes an object to The time it takes an object to spin once on its axis (a day on the planet)spin once on its axis (a day on the planet)

Revolution-Revolution- The time it takes to orbit The time it takes to orbit another body in space ( a year on a another body in space ( a year on a planet)planet)

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MercuryMercury

Closest planet to the Sun Closest planet to the Sun (Avg. distance = 50 million Km)(Avg. distance = 50 million Km) Smallest PlanetSmallest Planet Heavily cratered rocky surfaceHeavily cratered rocky surface (Looks like the moon)(Looks like the moon) Has almost no atmosphere or weatherHas almost no atmosphere or weather Wide range of temperatures due to its Wide range of temperatures due to its slow rotation (-173slow rotation (-173°C°C to 427 to 427°C)°C) Period of rotation = 59 days 16 hoursPeriod of rotation = 59 days 16 hours Period of revolution = 88 daysPeriod of revolution = 88 days No moons or ringsNo moons or rings

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VenusVenus Avg. distance from the Sun = 108 million KmAvg. distance from the Sun = 108 million Km Known as Earth’s sister planet due to its Known as Earth’s sister planet due to its

similar size, mass, & densitysimilar size, mass, & density Rocky surface featuring canyons, craters, Rocky surface featuring canyons, craters,

plains, & volcanic mountainsplains, & volcanic mountains Toxic atmosphere composed of sulfuric acid Toxic atmosphere composed of sulfuric acid

and COand CO2 2

The greenhouse effect produces an extremely The greenhouse effect produces an extremely high surface temperature (462high surface temperature (462°C)°C)

Period of rotation = 243 days (retrograde)Period of rotation = 243 days (retrograde) Period of revolution = 225 daysPeriod of revolution = 225 days No moons or rings No moons or rings

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EarthEarth

Avg. distance from the Sun = 150 million Avg. distance from the Sun = 150 million KmKm

Rocky surface, 70% of which is covered by Rocky surface, 70% of which is covered by water water

Only planet that has water in all three statesOnly planet that has water in all three states Atmosphere composed primarily of nitrogen Atmosphere composed primarily of nitrogen

and oxygenand oxygen Surface temperatures range from -90Surface temperatures range from -90°C to °C to

58°C58°C Period of rotation = 24 hoursPeriod of rotation = 24 hours Period of revolution = 365 ¼ daysPeriod of revolution = 365 ¼ days One moon, no ringsOne moon, no rings

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MarsMars Avg. distance from the Sun = 228 million KmAvg. distance from the Sun = 228 million Km About half the size of EarthAbout half the size of Earth Red colored surface is rocky, heavily cratered, Red colored surface is rocky, heavily cratered,

and features lava covered plains, a network of and features lava covered plains, a network of gouged out channels, huge inactive gouged out channels, huge inactive volcanoes, and polar ice capsvolcanoes, and polar ice caps

Thin atmosphere composed of COThin atmosphere composed of CO2 2 , nitrogen, , nitrogen, argon, oxygen, and water vaporargon, oxygen, and water vapor

Temperatures range from -87Temperatures range from -87°C to -5°C°C to -5°C Period of rotation = 24.5 hrs Period of rotation = 24.5 hrs Period of revolution = 1.88 yearsPeriod of revolution = 1.88 years Two moons, no ringsTwo moons, no rings

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JupiterJupiter Avg. distance from the Sun = 778 million KmAvg. distance from the Sun = 778 million Km Largest planetLargest planet Thought to have a small rocky core Thought to have a small rocky core

surrounded by layers of gaseous cloudssurrounded by layers of gaseous clouds Thick atmosphere composed of hydrogen, Thick atmosphere composed of hydrogen,

helium, methane, & ammoniahelium, methane, & ammonia Huge storms, like the great red spot, swirl Huge storms, like the great red spot, swirl

across the surface across the surface Surface temperature = -148Surface temperature = -148°C°C Period of rotation = 10 hoursPeriod of rotation = 10 hours Period of revolution = 11.86 yearsPeriod of revolution = 11.86 years 63 moons and one thin ring (per NASA)63 moons and one thin ring (per NASA)

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SaturnSaturn Avg. distance from the Sun = 1427 million Avg. distance from the Sun = 1427 million

KmKm Swirling clouds produce a banded lookSwirling clouds produce a banded look Ice particles form a series of rings around the Ice particles form a series of rings around the

planetplanet Atmosphere is stormy and composed of Atmosphere is stormy and composed of

hydrogen, helium, methane, and ammoniahydrogen, helium, methane, and ammonia Average surface temperature = -178Average surface temperature = -178°C°C Period of rotation = 10.5 hoursPeriod of rotation = 10.5 hours Period of revolution = 29.46 yearsPeriod of revolution = 29.46 years 56 moons, 7 major rings, & thousands of 56 moons, 7 major rings, & thousands of

ringlets (per NASA)ringlets (per NASA)

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UranusUranus

Avg. distance from the Sun = 2869 million KmAvg. distance from the Sun = 2869 million Km Gas giant that rotates on its sideGas giant that rotates on its side Thick bluish-green atmosphere composed of Thick bluish-green atmosphere composed of hydrogen, helium, & methanehydrogen, helium, & methane Avg. surface temperature = -216Avg. surface temperature = -216°C°C Period of rotation = 16.8 hours (retrograde)Period of rotation = 16.8 hours (retrograde) Period of revolution = 84 yearsPeriod of revolution = 84 years 27 moons and 9 narrow rings (per NASA)27 moons and 9 narrow rings (per NASA)

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NeptuneNeptune

Avg. distance from the Sun = 4486 million KmAvg. distance from the Sun = 4486 million Km Bluish colored gas giantBluish colored gas giant Huge clouds of methane float in an atmosphere of Huge clouds of methane float in an atmosphere of

hydrogen and heliumhydrogen and helium Avg. surface temperature = -214Avg. surface temperature = -214°C°C Period of rotation = 16 hoursPeriod of rotation = 16 hours Period of revolution = 164.8 yearsPeriod of revolution = 164.8 years 13 moons and 4 rings (per NASA)13 moons and 4 rings (per NASA)

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Other Objects in the Solar Other Objects in the Solar SystemSystem

Dwarf PlanetsDwarf PlanetsAsteroidsAsteroidsMeteoroidsMeteoroidsCometsCometsMoonsMoonsThe SunThe Sun

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Dwarf PlanetsDwarf Planets

Pluto and any other round object that "has not Pluto and any other round object that "has not cleared the neighborhood around its orbit, and is cleared the neighborhood around its orbit, and is not a satellite" not a satellite"

Ceres is the only dwarf planet in the asteroid beltCeres is the only dwarf planet in the asteroid belt Currently, there are three celestial bodies that Currently, there are three celestial bodies that

have been redefined by the International have been redefined by the International Astronomical Union (IAU) as dwarf planets Astronomical Union (IAU) as dwarf planets (Pluto, Ceres, & Eris)(Pluto, Ceres, & Eris)

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AsteroidsAsteroids Chunks of rock or Chunks of rock or

fragments of planet-fragments of planet-like material floating in like material floating in spacespace

Most are irregular in Most are irregular in shape and less thanshape and less than

1 Km long1 Km long Most revolve around Most revolve around

the Sun in a narrow the Sun in a narrow band, between Mars band, between Mars and Jupiter, called the and Jupiter, called the asteroid beltasteroid belt

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Meteoroids, Meteors, & MeteoritesMeteoroids, Meteors, & Meteorites

Meteoroids-Meteoroids- Chunks of metal or stone Chunks of metal or stone that orbit the Sunthat orbit the Sun

- Most come from the asteroid- Most come from the asteroid belt or from comets that have belt or from comets that have

broken upbroken up- About 100 million enter the - About 100 million enter the

Earth’s atmosphere dailyEarth’s atmosphere daily Meteors-Meteors- Streaks of light produced when Streaks of light produced when

meteoroids burn up as they enter our meteoroids burn up as they enter our atmosphereatmosphere

Meteorite-Meteorite- A meteoroid that strikes the A meteoroid that strikes the Earth’s surface (Can produce craters) Earth’s surface (Can produce craters)

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CometsComets

Object made of ice, Object made of ice, gas, and dust that orbit gas, and dust that orbit the Sunthe Sun

There are three parts to There are three parts to a comet; a nucleus, a a comet; a nucleus, a coma, and a tailcoma, and a tail

Most comets originate Most comets originate in a dense cloud, called in a dense cloud, called the Oort Cloud, which the Oort Cloud, which lies beyond Plutolies beyond Pluto

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The MoonThe Moon

Earth’s closest neighbor in spaceEarth’s closest neighbor in space

(Avg. distance = 384,403 Km)(Avg. distance = 384,403 Km) About ¼ the size of the EarthAbout ¼ the size of the Earth Has 1/6 of the gravity of the EarthHas 1/6 of the gravity of the Earth It is dry, airless, and barrenIt is dry, airless, and barren

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Movement of the MoonMovement of the Moon

Revolves around the Earth in a Revolves around the Earth in a counter-clockwise directioncounter-clockwise direction

Rises in the east and sets in the Rises in the east and sets in the west (about 50 minutes later each west (about 50 minutes later each day)day)

Period of revolution and rotation Period of revolution and rotation are both 27.3 days (Causes the are both 27.3 days (Causes the same side of the moon to always same side of the moon to always face the Earth)face the Earth)

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The Moon’s Phases The Moon’s Phases

The relative motions of the Earth, Moon and The relative motions of the Earth, Moon and Sun cause a change in the moon’s appearanceSun cause a change in the moon’s appearance

The Sun lights up the half of the Moon that The Sun lights up the half of the Moon that faces itfaces it

The lighted portion of the Moon appears to The lighted portion of the Moon appears to change dailychange daily

The daily changes in the Moon’s appearance The daily changes in the Moon’s appearance are called are called phasesphases

Lunar month- Lunar month- Time from one new moon to the Time from one new moon to the next (about 29.5 days)next (about 29.5 days)

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Phases of the MoonPhases of the Moon

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Phases of the MoonPhases of the Moon

Waxing PhasesWaxing Phases

When the moon appears to grow larger as it goes When the moon appears to grow larger as it goes

from being a new moon to a full moonfrom being a new moon to a full moon•New moon•New (waxing) crescent•First quarter•New (waxing) gibbous•Full Moon

Waning PhasesWaning Phases

When the moon appears to grow smaller as it When the moon appears to grow smaller as it

goes from the full moon phase to the new moongoes from the full moon phase to the new moon

•Full moon•Old (waning) gibbous•Last quarter•Old (waning) crescent•New moon

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EclipsesEclipses Occur when one object in Occur when one object in

the sky is blocked from view the sky is blocked from view by another by another

Named for the object that Named for the object that we don’t seewe don’t see

During an eclipse, the During an eclipse, the shadow of one object falls shadow of one object falls on the otheron the other The shadow has two parts, a The shadow has two parts, a

dark inner shadow (dark inner shadow (umbraumbra) ) and a lighter outer shadow and a lighter outer shadow ((penumbrapenumbra))

Being in the umbra produces a Being in the umbra produces a total eclipsetotal eclipse, while being in the , while being in the penumbra, a penumbra, a partial eclipsepartial eclipse

Lunar EclipseLunar Eclipse

Blocking of the moon that takes place when Earth Blocking of the moon that takes place when Earth

comes directly between the Sun and the full mooncomes directly between the Sun and the full moon

Solar EclipsesSolar Eclipses

Blocking of the Sun that occurs when the new moon Blocking of the Sun that occurs when the new moon

comes directly between the Sun and the Earthcomes directly between the Sun and the Earth

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StarsStars

There may be as many as 200 billion, There may be as many as 200 billion, billion stars in the universe billion stars in the universe (200,000,000,000,000,000,000)(200,000,000,000,000,000,000)

Stars differ in size,Stars differ in size,

mass, color, mass, color,

temperature, and temperature, and

brightnessbrightness

Stars are divided into 5 main Stars are divided into 5 main groups according to sizegroups according to size

Neutron stars-Neutron stars- the smallest stars the smallest stars (avg. diameter = 16 km)(avg. diameter = 16 km)

White dwarfs-White dwarfs- smaller than the Earth smaller than the Earth (ex. Van Maanen’s star)(ex. Van Maanen’s star)

Medium-sized stars-Medium-sized stars- vary in size from vary in size from 1/10 to 10 times the size of the Sun 1/10 to 10 times the size of the Sun (ex. the Sun & Sirius)(ex. the Sun & Sirius)

Giant stars-Giant stars- 10 to 100 times as large as 10 to 100 times as large as the Sun (ex. Aldebara)the Sun (ex. Aldebara)

Supergiant stars-Supergiant stars- up to 1000 times larger up to 1000 times larger than the Sun (ex. Rigel & Betelgeuse)than the Sun (ex. Rigel & Betelgeuse)

Smallest

Largest

Composition of StarsComposition of Stars

Spectroscopes are used to determine the Spectroscopes are used to determine the composition of starscomposition of stars

Almost all stars have the same Almost all stars have the same compositioncomposition

60 - 80% hydrogen60 - 80% hydrogen20 – 30% helium20 – 30% helium

Temperature of StarsTemperature of Stars

The color of stars can be used to determineThe color of stars can be used to determine

their surface temperaturetheir surface temperatureBlueBlue = 35,000 = 35,000°C°CWhite = 10,000°CWhite = 10,000°CYellowYellow = 6,000°C = 6,000°CRed-orangeRed-orange = 5,000°C = 5,000°CRedRed = 3,000°C = 3,000°C

The temperature at the center of a star is much greater thanat its surface

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Brightness of StarsBrightness of Stars

The brightness of a star depends on its The brightness of a star depends on its size, its surface temperature, and its size, its surface temperature, and its distance from Earthdistance from Earth

Apparent magnitude-Apparent magnitude- the brightness of a the brightness of a star as it appears from Earthstar as it appears from Earth

Absolute magnitude-Absolute magnitude- the amount of light the amount of light a star actually gives offa star actually gives off

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Hertzsprung-Russell DiagramHertzsprung-Russell Diagram

A chart that shows the relationship A chart that shows the relationship between the absolute magnitude and the between the absolute magnitude and the surface temperature of starssurface temperature of stars

As the absolute magnitude of stars As the absolute magnitude of stars increases, the temperature usually increases, the temperature usually increases as wellincreases as well

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Evolution of StarsEvolution of Stars

Stars evolve, or change, over timeStars evolve, or change, over timeThe amount of mass a star begins with is The amount of mass a star begins with is

the main factor that determines its the main factor that determines its evolutionevolution

The different kinds of stars in the sky The different kinds of stars in the sky represent the various stages in the life represent the various stages in the life cycle of stars cycle of stars

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Stages in the Life Cycle of Stars Stages in the Life Cycle of Stars All stars are created from the gases in a nebulaeAll stars are created from the gases in a nebulae When temperatures reach 15,000When temperatures reach 15,000°C, nuclear fusion °C, nuclear fusion

begins and the begins and the protostarprotostar begins to shine begins to shine For the first few billion years the star continues to shine For the first few billion years the star continues to shine

as its hydrogen is changed to helium as its hydrogen is changed to helium The evolutionary path of a star depends on its massThe evolutionary path of a star depends on its mass

Medium-sized starsMedium-sized stars Expand to Expand to red giantsred giants white dwarfswhite dwarfs dims to a dims to a black dwarfblack dwarf or or dead stardead star

Massive starsMassive stars Expand to Expand to red giantsred giants or or supergiantssupergiants explode in a explode in a supernovasupernova become a become a neutron starneutron star or a or a black black hole hole (depending on initial mass) (depending on initial mass)

Possible Evolutionary Paths for StarsPossible Evolutionary Paths for Stars

ConstellationsConstellations

Groups of stars that form a patternGroups of stars that form a pattern The revolution of the Earth around the Sun The revolution of the Earth around the Sun

cause different constellations to be seen at cause different constellations to be seen at different times of the yeardifferent times of the year

Stars located above the north and south poles, Stars located above the north and south poles, called called circumpolar starscircumpolar stars, appear to move in , appear to move in circles above the horizon each night circles above the horizon each night

Astronomers use constellations as landmarks to Astronomers use constellations as landmarks to locate other objects in the skylocate other objects in the sky

Constellations in the AutumnConstellations in the Autumn SkySky

Optical TelescopesOptical Telescopes

Tools that use large lenses or mirrors to gather Tools that use large lenses or mirrors to gather rays of light from a star and focus it in one spotrays of light from a star and focus it in one spot

The light-gathering power depends on the area The light-gathering power depends on the area of its lens or mirror (the greater the area, the of its lens or mirror (the greater the area, the more light it can gather)more light it can gather)

Have three basic functionsHave three basic functions1.1. Collect more light than the naked eyeCollect more light than the naked eye

2.2. Separate distant objects from one anotherSeparate distant objects from one another

3.3. Magnify imagesMagnify images

Refracting TelescopesRefracting Telescopes

Use convex lenses to gather light Use convex lenses to gather light The lensesThe lenses

refractrefract (bend) (bend)

the rays of the rays of

light to formlight to form

an imagean image

Reflecting TelescopesReflecting Telescopes Use mirrors to gather and focus lightUse mirrors to gather and focus light

Types of Optical TelescopesTypes of Optical Telescopes

How Light BehavesHow Light Behaves

Light travels in straight-line paths called raysLight travels in straight-line paths called rays

Reflection- Reflection- When light strikesWhen light strikes

a surface, some of it bounces a surface, some of it bounces

backback

Refraction-Refraction- The bending of The bending of

light due to a change in speedlight due to a change in speed

Mirrors Reflect LightMirrors Reflect Light Mirrors are classified based on the shape of their Mirrors are classified based on the shape of their

surfacesurface Plane mirrors-Plane mirrors-

Perfectly flat surfacesPerfectly flat surfaces Image appears to be on the other side of the mirrorImage appears to be on the other side of the mirror

Concave mirrors-Concave mirrors- Surface curves inwardSurface curves inward Reflect light rays to the same point in front of the mirror Reflect light rays to the same point in front of the mirror

(focal point)(focal point) Convex mirrors-Convex mirrors-

Surface curves outwardSurface curves outward Reflected rays spread out from the surface of the mirrorReflected rays spread out from the surface of the mirror

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Types of MirrorsTypes of Mirrors

Lenses Refract LightLenses Refract Light Convex lenses-Convex lenses- Lenses that are thicker in the Lenses that are thicker in the

center than at the edgescenter than at the edges Bend rays of light toward the thicker centerBend rays of light toward the thicker center of the lensof the lens The amount of refraction depends on how The amount of refraction depends on how much the lens curves (the greater the curve,much the lens curves (the greater the curve, the more the light is refracted)the more the light is refracted) Converge light rays at the focal pointConverge light rays at the focal point

Concave Lenses-Concave Lenses- Lenses that are thinner in the Lenses that are thinner in the center than at the edgescenter than at the edges

Bend rays of light outward toward the Bend rays of light outward toward the thicker ends of the lensthicker ends of the lens Diverge rays of lightDiverge rays of light

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Types of LensesTypes of Lenses