Lecture 4Outline of Last Lecture I. Conservation of EnergyII. TemperatureIII. Temperature and DensityIV. Heat EnergyV. Phases of WaterVI. Phase ChangesVII.Heat TransferVIII. Solar HeatingIX. Rising Air and TemperatureOutline of Current Lecture X. The Electromagnetic SpectrumXI. Electromagnetic WavesXII. Radiation and TemperatureXIII. Solar SpectrumXIV. Radiation and ColorXV. Radiation BudgetXVI. Radiation and AtmosphereXVII. Greenhouse EffectXVIII. Why is the Sky Blue?Current LectureXIX. The Electromagnetic Spectruma. Radio/TV Waves (not very energetic)ATMS 100 1st Editionb. Microwaves (not very energetic)c. Infrared Radiationd. Visible Light (we can see)e. Ultraviolet Radiation (we cannot see; more energy than visible light)f. X-rays (very energetic)g. Gamma Rays XX. Electromagnetic Wavesa. Visible Spectrumb. shorter wavelength=greater energyi. blue/violet=most energeticii. red=least energeticc. 1 um= 10^6 m (1 millionth of a meter)i. 1/100th of a human haird. Speed= 3.0 X 10^8 m/s= 186,000 miles/secXXI. Radiation and Temperaturea. all objects emit radiation at all timesi. at earth temperatures, this is IR radiationb. objects with higher temperatures emit shorter wavelength (more energy/more radiation) electromagnetic wavesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c. radiation intensity increases with temperatured. objects that are hot enough emit visible lighti. red hot, white objectsii. the suniii. objects emit radiation of many different wavelengthsXXII. Solar Spectruma. the sun primarily emits visible light (shortwave radiation)i. 160,000 times more radiation than the earth (per unit area)b. the earth emits infrared (longwave) radiation invisible to humansXXIII. Radiation and Colora. most colors originate due to reflected lighti. green objects absorb all wavelengths except green, which is reflectedb. darker objects absorb many colors (absence of color)i. trees, asphalt, dark roofs, black carsii. warm quickly in sunc. lighter objects reflect more colorsi. snow, white pavement, light sandii. tend not to warm as fast in sund. Earth’s surface and the sun absorb and emit radiation at many wavelengthsi. called blackbodiesXXIV. Radiation Budgeta. Why do you feel hotter when you are in the sun?i. your body (or the earth) receives more energy than it emits, so temperature increasesb. Why does the temperature usually drop at night?i. the earth emits more energy than it receives, so its tem-perature decreasesc. if an object absorbs more radiation than it emits:i. temperature increasesd. if an object emits more radiation than it absorbsi. temperature decreasese. if an object emits and absorbs the same amount of radiationi. temperature remains the same1. this is called radiative equilibrium temperatureXXV. Radiation and the Atmospherea. Earths radiative equilibrium temperature is -18 C i. does not account for atmosphereb. actual average surface temperature is 15 Ci. why the difference? atmosphere does not behave as black-bodyii. many gases only absorb/emit radiation at certain wave-lengthsXXVI. Greenhouse Effectsa. certain gases absorb radiation at certain wavelengthsi. radiant energy is converted to thermal energy- these gasesheat upii. these gases emit mor IR radiation-both upward (to space) and downward (to the surface)iii. known as atmospheric greenhouse effectb. how does agricultural greenhouse work?i. sunlight enters glass top-- sunlight ground, which heats air--glass stops hot air from escapingXXVII. Incoming solar radiationa. three processes can happen to radiation in the atmosphere:i. Absorption1. Example: ozone absorbs UV radiationii. Scattering1. light hits air molecules, dust, or clouds and goes in all directionsiii. Reflection1. like scattering, but most radiation goes backwardsXXVIII. Albedoa. measure of reflectivityb. equal to reflected radiation dived by total incoming radiationc. selected albedos:i. snow= 75-95%ii. earth and atmosphere= 20%XXIX. Why is the Sky Blue?a. air molecules scatter 4 times more blue light than red lightb. if we look away the sun, we see four times as much blue light than red lightc. water appears blue because it reflects from the