Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine [email protected] HoursHomeworkHW #5HW #6Slide 7Messenger just flew by MercuryEnergyConservation of EnergyEnergy unitsSlide 123 basic categories of energyKinetic energySlide 15AnswerThermal energy (kind of kinetic energy)Temperature scalesIn ScienceSlide 20Slide 21Gravitational Potential EnergySlide 23Slide 24Converting Mass to EnergyE = mc2Who came up with it?Slide 28Slide 29Slide 30Mass-EnergySlide 32LightSlide 34Slide 35Particle aspectPhotonsWave aspectThomas Young ExperimentCharacteristics of wavesFor lightCalculationsSlide 43Energy of lightSlide 45ROYGBIVSlide 47Slide 48Slide 49So why are some types of radiation dangerous?Slide 51When you measure an astronomical bodyMatterAtomsSlide 55Slide 56ElementsChargeSlide 59DefinitionsAny Questions?Astronomy 101The Solar SystemTuesday, Thursday2:30-3:45 pmHasbrouck 20Tom [email protected]•Course Website:–http://blogs.umass.edu/astron101-tburbine/•Textbook:–Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny.•You also will need a calculator.Office Hours•Mine•Tuesday, Thursday - 1:15-2:15pm•Lederle Graduate Research Tower C 632•Neil•Tuesday, Thursday - 11 am-noon •Lederle Graduate Research Tower B 619-OHomework•We will use Spark•https://spark.oit.umass.edu/webct/logonDisplay.dowebct•Homework will be due approximately twice a weekHW #5•Due todayHW #6 •Due Tuesdayhttp://www.post-gazette.com/pg/09271/1000779-369.stmMessenger just flew by Mercuryhttp://www.msnbc.msn.com/id/33092470/ns/technology_and_science-space/Energy•Energy is the ability to generate motionConservation of Energy•Energy is neither created or destroyed – it just changes forms•Conservation of Energy–The energy in a closed system may change form, but the total amount of energy does not change as a result of any process.Energy units•In English Units, we use calories to measure energy•In science (and in this class), we will use joules to measure energy•1 Joule = 1 kg*m2/s23 basic categories of energy•Kinetic energy – energy of motion•Potential energy – energy being stored for possible conversion into kinetic energy•Radiative energy – energy carried by lightKinetic energy•Kinetic energy = ½ mv2•m is mass in kg•v is velocity in meters/s•Remember: a joule has units of kg*m2/s2•How much kinetic energy does a 2 kg rock have if it is thrown at 20 m/s?•Kinetic energy = ½ mv2•A) 200 J•B) 400 J•C) 40 J•D) 800 JAnswer•KE = ½ * 2 * (20) *(20) = 400 joulesThermal energy (kind of kinetic energy)•Temperature is a measure of the average kinetic energy of the particles•Higher temperature – more kinetic energy, particles moving faster•For examples, air molecules around you are moving at ~600 m/shttp://eo.ucar.edu/webweather/molecules.htmlTemperature scales•In America, we use Fahrenheit•Water freezes at 32 degrees F•Water boils at 212 degrees F•Everywhere else, they use Celsius•Water freezes at 0 degrees C•Water boils at 100 degrees CIn Science•Temperature is measured in Kelvin•Zero Kelvin is absolute zero – nothing moves•Add 273.15 to the Celsius temperature to get the Kelvin temperature•273.15 Kelvin = 0 degrees CelsiusGravitational Potential Energy•Gravitational Potential Energy released as an object falls depends on its mass, the strength of gravity, and the distance it falls•For example, your gravitational potential energy increases as you go farther up in the air•This is because you hit the ground at a faster speed if you jump from a higher distanceGravitational Potential Energy•PE = -G m*M/r•G is the Gravitational constant•m is mass of one body•M is mass of second body•r is distance (people also use variable d)•KE + PE = 0•As kinetic energy increases, potential energy decreasesConverting Mass to Energy•What is the most famous formula in the world?E = mc2•m is mass in kilograms•c is speed of light in meters/s (3 x 108 m/s)•So E is in joules•very small amounts of mass may be converted into a very large amount of energy andWho came up with it?•How much energy can be produced if you can convert 10 kg of material totally into energy?•E = mc2•A) 3.0 x 108 J•B) 3.0 x 1016 J•C) 9.0 x 1017 J•D) 9.0 x 1010 JAnswer•E = 10 kg * (3 x 108 m/s) * (3 x 108 m/s)•E = 10* (9 x 1016) J•E = 90 x 1016 J•E = 9.0 x 1017 JMass-Energy•E=mc2•So Mass is a form of potential energy•Where is one place where you see mass converted into energy?Light•Light is a form of energyLight•These are all forms of light–Gamma rays–X-rays–Ultraviolet light–Visible light–Infrared light–Radio wavesLight•Can act as a particle•Can also act as a waveParticle aspect•Particles called photons stream from the Sun and can be blocked by your bodyPhotons•Light is quantized•Comes in discrete packets called photonsWave aspectThomas Young Experiment•http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/Characteristics of waves•velocity = wavelength x frequency•Wavelength = distance•Frequency = cycles per second = hertzFor light•c = wavelength x frequency•In vacuum, speed of light stays the same•So if wavelength goes up•Frequency does down•f = frequency•λ = wavelength•c = λ x fCalculations•c = λ x f•So if the wavelength is 1 x 10-12 m•3 x 108 m/s = 1 x 10-12 m * f•f = 3 x 108 m/s/1 x 10-12 m •f = 3 x 1020 s-1 = 3 x 1020 HzCalculations•c = λ x f•So if the frequency is 1 x 1015 Hz•3 x 108 m/s = λ * 1 x 1015 Hz •λ = 3 x 108 m/s/1 x 1015 Hz •λ = 3 x 10-7 mEnergy of light•Energy is directly proportional to the frequency•E = h * f•h = Planck’s constant = 6.626 x 10-34 J*s•since f = c/λ•Energy is inversely proportional to the wavelength•E = hc/λHigher the frequency, Higher the energy of the photonHigher the wavelength, Lower the energy of the photonredvioletVIBGYORROYGBIV •ROYGBIV •Red – long wavelength•Violet – short wavelengthhttp://www.arpansa.gov.au/images/basics/emr.jpgCalculations•What is the energy of a radio wave with a frequency of 1 x 107 Hz?•E = h * f•h = Planck’s constant = 6.626 x 10-34 J/s•E = 6.626 x 10-34 J/s * 1 x 107 •E = 6.626 x 10-27 JCalculations•What is the energy of a gamma ray photon with wavelength of 1 x 10-15 m•E = hc/λ•h = Planck’s constant = 6.626 x 10-34 J/s•E = 6.626 x 10-34
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