Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Review: Kepler's LawsReview: Newton's Laws of MotionOrbit of Earth around SunGravity and OrbitsCorrection to Kepler’s Third LawQuestionThat one was complicated, because we need to remember:Chapter 2: EM WavesSlide 26Slide 27Slide 28Electric Force - opposites attract, likes repel Oscillating charges radiate All objects have temperatures greater than absolute zero - random thermal motion All objects radiate! Why don’t we see the radiation coming from many ordinary objects? Dog whistle analogySlide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Info for the TestBring a #2 pencil.No electronic devices: No cell phones, headphones, etc.No books, notes, etc.No hats.Grades will be posted on the course website.StudyingStudy questions on website highlight important topicsKnow definitions of BOLD terms in chapter summariesQuestions from lectures will give you some idea of what questions I may ask - I may reuse or slightly modify some of these!This review will focus on the more complex topics we have gone overThis review will not cover everything from the lectures and textThe "Solar Day" and the "Sidereal Day" Solar Day How long it takes for the Sun to return to the same position in the sky (24 hours).Sidereal Day How long it takes for the Earth to rotate 360o on its axis.These are not the same! Which is longer? Why?One solar day later, the Earth has rotated slightly more than 360oA solar day is longer than a sidereal day by 3.9 minutes.(24 hours vs. 23 hours 56 minutes 4.091 seconds)Difference due to rotation and revolution of Earth.The Earth's SeasonsWhy does the Earth have seasons?How is this related to how high the Sun rises in the sky in Summer? In Winter?Seasons: Due to tilt of Earth's Axis of RotationSummerWinterIn winter, the sun never gets very high in the sky => each bit of ground receives less radiation => coolerSeasons caused by tilt of Earth’s axis of rotation.Earth is farthest from sun during summer.-What motion of the Earth acts to slowly change the orientation of the Earth's axis of rotation?-How long does one cycle of this motion take?PrecessionEarthMoonSpin axis**VegaPolarisPrecession Period 26,000 years!ParallaxHow does the parallax angle vary with the distance to the foreground object?How does the parallax angle vary with the length of the baseline?Parallax angle:Decreases with distance to the foreground object.Increases with the length ofthe baseline.EclipsesDuring which phase(s) can a lunar eclipse occur?What about a solar eclipse?How do the angular diameters of the moon and the Sun compare and how do we know?Geocentric vs. Heliocentric ModelsThe geocentric model explained the retrograde motion of the planets by introducing _______?The geocentric model was finally abandoned because it was unable to explain the observed ______ of Venus.12345671234567EarthMarsApparent motion of Mars against "fixed" stars.******JanuaryJulyGeocentric model fails to account for phases of VenusHeliocentric model easily accounts for phases of VenusReview: Kepler's Laws1. Planets travel aound the sun in elliptical orbits with the sun at one focus of the ellipse.2. A line connecting the Sun and a planet sweeps out equal areas in equal times.3. The square of a planet's orbital period is proportional to the cube of its semi-major axis. (P2 α a3)Review: Newton's Laws of Motion1. Every object continues in a state of rest or a state of uniform motion in a straight line unless acted on by a force. (Inertia)2. F = m*a3. For every action there is an equal and opposite reaction.Newton's Law of Gravity: F =G m1 m2 R2Orbit of Earth around SunGravity and Orbits•Throwing an object fast enough will put the object into orbit! (Neglecting air resistance)•Moon is continually “falling” towards the Earth in its orbit (Gravity vs. inertia)Correction to Kepler’s Third LawEarth and sun actually rotate about their common center of massCorresponds to a point inside sunUsed to detect extrasolar planetsQuestion The acceleration experienced by a falling object due to Earth's gravity _____ the mass of the object.A) increases withB) decreases withC) is independent ofThat one was complicated, because we need to remember:Fg =G m mE R2ANDa = FgmSo, a =G m mE m R2=G mE R2Chapter 2: EM WavesWhat is a wave?What are the main properties of waves?What two things do all waves transport?Waves are a type of disturbance that can propagate or travel.Waves carry information and energy.Properties of a wavewavelength ()crestamplitude (A)velocity (v)trough is a distance, so its units are m, cm, or mm, etc.Period (T): time between crest (or trough) passagesFrequency (f): rate of passage of crests (or troughs), f v = f1T(units: Hertz or cycles/sec)Equilibrium positionAll radiation (including visible light) travels as Electromagnetic waves.That is, waves of electric and magnetic fields travelling together.What are some examples of objects with magnetic fields:What are some examples of objects with electric fields:All radiation (including visible light) travels as Electromagnetic waves.That is, waves of electric and magnetic fields travelling together.What are some examples of objects with magnetic fields:a bar magnetthe Earththe SunWhat are some examples of objects with electric fields:}"charged" particles that make up atoms.Anything with too many or to few electrons!Electrical appliancesLightningProtonselectronsElectric Force - opposites attract, likes repelOscillating charges radiateAll objects have temperatures greater than absolute zero - random thermal motionAll objects radiate!Why don’t we see the radiation coming from many ordinary objects?Dog whistle analogyWhat is the radiation spectrum displayed by most astronomical objects called?What property of the spectrum tells us the temperature of the object?"cold" dust"hot" stars"cool" starSunfrequency increases, wavelength decreasesOverall shape of blackbody curve is the SAME for objects at ALL temperatures!Emission and Absorption SpectraHow are the emission and absorption spectra of a certain element related?How do the emission (or absorption) spectra of two different elements compare?For a given element, emission and absorption lines occur at the