McGraw-Hill Ch 1, 3, 4 (The Cycles of the Sky, Gravity and Motion, Light and Atoms )
McGraw-Hill Ch 1, 3, 4 (The Cycles of the Sky, Gravity and Motion, Light and Atoms ) PHYS 1152 01
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This 7 page Bundle was uploaded by Christa White on Wednesday September 9, 2015. The Bundle belongs to PHYS 1152 01 at Idaho State University taught by Dr. Bryan Barclay in Fall 2015. Since its upload, it has received 34 views. For similar materials see Descriptive Astronomy in Physics 2 at Idaho State University.
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Date Created: 09/09/15
Descriptive Astronomy PHYS 1152 CH 4 Light and Atoms Properties of Electromagnetic Waves Atoms a each kind has a unique number electrons and of protons in the nucleus b each kind has a different set of energy levels or orbitals Element of of Protons Neutrons Hydrogen 1 O 1 Helium 2 2 1 Carbon 6 6 7 Nitrogen 7 7 8 Oxygen 8 8 10 9 Neon 1O 101112 Silicon 14 14 15 16 Iron 26 30 31 32 Note the of protons is determines the kind of chemical element the atom is protons part of the nucleus of an atom positive charge neutrons also T T neutral charge electrons orbits the nucleus of an atom negative charge quantized an electron s orbital radius must be proportionate to the other electrons of that atom conservation of enerov energy can never be created or destroyed it simply changes form emission energy released when an electron jumps from a higher to a lower orbital hvdrooen atoms can emit red light and blue light because their electron transfers vary for example a small amount of energy emitted in a short transfer will produce a more red photon and a large amount will produce a more blue photon absorption energy preserved when an electron is lifted from a lower to a higher orbital exciting the atom and thus increasing the election s energy blackbody an object that absorbs all the radiation falling upon it electromagnetic wavesspectrum longestgtshortest radio waves audible gt infrared light detected as heat gt visible light gt ultraviolet light gt X rays used to probe for medical or scientific purposesgt gamma rays associated with supernova explosions etc Note the only difference between each of these is their wavelength Measurements wavelength distance between crests in a lightwave because wl determines the colors we can see the wavelength quantity is used to imply the color of the light wl also determines how much energy is carried by electromagnetic radiation frequency of wave crests that pass a point in some time interval usually 1 sec nanometer used to measure wavelengths equivalent to one billionth of a meter K Greek letter nu that denotes hertz Hz a unit used to measure frequency L Greek letter lambda that denotes nanometers nm a unit used to measure wavelength Planck s Constant 663 x 10quot34 joulesecond joulesecond mquot2kg s Enerav carried bv a photon E hcA Eenergy h Planck s constant C speed of light also constant A wavelength Note from this formula we have learned that shortwavelength photons carry proportionally more energy than longwavelength photons The Models because of lights waveparticle duality scientists use each respective model depending on which best describes the phenomenon they are trying to explain photons packets of energy that enter your eye and produce the sensation of light associated with the Particles Model waveparticle dualitv the fact that many properties of light are either easiest described as waves or easiest described as particles Waves Model a light is a combination of electric and magnetic energy fields b best describes the phenomenon of the focusing of light by a lens Particles Model a light is a stream of particles known as photons b best describes the phenomenon of light reflecting off a mirror photons strike mirror and bounce back Properties of Light a can travel through air and water but do not need a medium to reach us b travel at about 300000 kmsec and moves at a constant speed in empty space c the spectrum of an object can be used to identify what elements it contains because element emits or absorbs a unique set of spectra line colors light a mix of electric and magnetic energy aka electromagnetic wavesradiation white light ex sunlight not a separate color of light but a mixture of all colors in which not one is dominant Relationship Between Frequency Wavelength and Wave Speed Avc Awavelength vwave frequency cspeed of light a constant Note if v is in hertz the units of A will be set by the units you choose for c For example if c is in meters per second A will be in meters Doppler shift a change in the wavelength of light coming from an object because the object is moving a redshifts shifts that increase the measured wavelength occurs when the distance between the source and the observer is increasing b blueshifts shifts that decrease the measured wavelength occurs when the distance is decreasing Donler Shift Formula Vc A Am An CAA An V velocity of source along the line of sight radial velocity c speed of light constant A measured wavelength An emitted wavelength AA wavelength shift Wien s Law as an object s temperature increases the object radiates light more strongly at shorter wavelengths spectrums a continuous created by a hot dense substance b absorptionline almost all colors are present but specific colors are dimmissing formed by cooler gases c emissionline only specific colors are preset formed by hot thin gases temperature can be measured in Celsius Fahrenheit Kelvins 0 Kelvins 273 C 460 F Descriptive Astronomy PHYS 1152 CH 1 The Cycles of the Sky Vocab constellation grouping of stars that represent a story or symbol of consequence to a culture there are 88 internationally recognized revolution Earth s orbit around the Sun rotation one spin of the Earth 360 on it s axis This rotation is tilted on the axis which is responsible for seasons and also responsible for the appearance of the Sun rising and setting ecliptic a line that projects the Earth s orbit onto the celestial sphere and traces the path as appeared on Earth of the Sun over a year Name origin comes from the fact that an eclipse can only occur when a new or full moon crosses it the ecliptic equinox occurs in March and September in which daytime and nighttime are of equal length the Sun rises due east and sets due west and crosses the celestial equator in the celestial sphere solstice occurs in June shortest night and December longest night At winter solstice the Sun is at its southernmost point on the celestial sphere and vice versa at summer solstice scienti c model descriptions that make the universe easier to understand ex the celestial sphere circumpolar star as viewed from a given latitude on Earth never setdisappears below the horizon due to it s proximity to one of the celestial poles heliocentric means the planets are centered and evolve around the Sun as opposed to the outdated geocentric belief that all planets revolved around the Earth Celestial Sphere creates a convenient way to describe the location of celestial bodies and visualize their motions North Celestial lPDle South cellesiial Plule a helps describe why the sun stars near the celestial equator the moon and plants such as Jupiter appear to rise in the east and set in the west b helps describe why the sunset appears farthest north during the summer solstice and farthest south during the winter solstice c helps describe why a single person in any fixed location can only see one hemisphere of the complete night sky at one time Can be misleading because a it implies that all the stars planets and Sun are on the same plane when they are truly all at greatly varying distances b puts the Earth at the center of the universe when truly our universe is heliocentric Constellations a many represent animals or heroes and have cultural meanings b have not changed significantly for thousands of years c the time when most clear in the night sky is when the Earth is directly between the Sun and that constellation Examples Libra June 1 Capricornus August 1 Taurus December 1 Virgo April 1 Other Tips Cause Earth s tilt Effect the North Pole experiences daylight for 6 months the Sun appears to move north and southchange declination on the celestial sphere rather than continuing to rise due east every day Cause Living between 235 north and 235 south near the celestial equator Effect twilights may seem shorter some days Sun may appear directly overhead In the Northern Hemisphere Hottest to Coldest 1 6 wks after summer solstice 2 summer solstice 3 spring equinox 4 winter solstice 5 6 weeks after winter solstice Cause Distance and how much light produces Effect the brightness of a star Cause Living above latitudes above 665 N Arctic Circle below 665 8 Antarctic Circle Effect experience 24 hours of daylight for part of the year Descriptive Astronomy PHYS 1152 CH 3 Gravity and Motion escape velocity ZGMIR 2 Ggravitational constant Mmass Rradius In order for a rocket to break free of a planet s gravitational pull must achieve at least this critical speed Of two objects with the same radius the one with larger mass will have the larger escape velocity Of two objects of the same mass the one with the smaller radius will have the larger escape velocity Use determines the velocity necessary to carry out explorations launch rockets from the Earth to remote space or to disengage any body of mass restricted by gravitational force Kepler s Third Law aquot3Pquot2 a P period Use relates the period and semimajor axis of orbits Newton s Law of Gravity F GMmIdAZ Fstrength of gravitational force between two bodies Mmass of one body mmass of second body dseparation between bodies center radius of the orbit G gravitational constant constant found by measuring the force between two bodies of known mass and separation Every mass exerts a force of attraction on every other mass The strength of the force is directly proportional to the product of the masses divided by the square of their separation Use relates mass distance and gravitational force using a constant Newton s Second Law of Motion a Flm a acceleration F force m mass Use relates force and acceleration Newton s Third Law of Motion F A on B F B on A F force A and B bodies respectively When two objects interact they create equal and opposite forces on each other Note that while the forces exerted may be equal and opposite the resulting magnitude of the acceleration is not necessarily the same Also a respective responding force only acts on one body the two bodies only create equal and opposite forces on each other Use law of action and reaction Vocab acceleration a a change in speed direction or both the result of forces includes increasing speed stopping speed and turning force F something that causes a change in speed direction or both velocity V the speed and direction of an object a vector quantityspeed and direction mass M or m the amount of matter in an object The measurement of mass is not affected by gravity surface gravity g the acceleration of gravity near a planet s surface 98msquot2 on Earth Has an affect on the weight of a personobject gravitational constant G a constant in Newton s law of gravity essentially IS gravity inertia essential to Galileo s laws of motion the tendency of an object in motion to stay in motion in a straight line and constant speed or an object at rest to stay at rest Using Orbital Motion to Measure an Object s Mass Ex Using the Earth s Gravitational Pull on the Moon to Measure the Mass of the Earth 1 The moon must be in circular orbit why 2 Because the moon is in circular orbit the force of gravity provides the force that makes the moon orbit 3 F orbit F gravity means mmoon XVA2d Gmmoon X Mplanetdquot2 4 Solving for V mmoon cancels out and MplanetVquot2dG Galileo a falling objects are accelerated at the same rate b the force of gravity is larger for more massive objects c the force of gravity is smaller at distances that are compared to the Earth s radius
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