A rope lifts a bucket at a constant speed. (Ignore air resistance.)
Week11 Monday,October30,2017 11:25AM Lecture18 Reflectionandreaction EnergyinEMwaves EMwavescarryenergythroughspaceatc EnergyfluxSav=ε0E m2=u cavndirectionofwavevectork Brightnessisduetointensityav =av ∝Em2 Pointlightsource:av (r)=∝1/r EMwavesalsocarrym2mentumandexertpressure p=u av=S av indirectionofk Radiationpressure:pc=uavIavc Reflectedpressure:2Iavc=twicepressurefromabsorbingsurface HotobjectemitEMwavesacrossmanyfrequencies Brightnessandfrequencyemissionincreaseastemperatureincreases Quantummechanics:energyinEMwavesreallycarriedasparticlelike"clumps"called photons