PHYS 112 Lecture 13: Part 2 (Electromagnetic Waves)
Document Summary
Electromagneticwaves egreleasedin lightning astaticdistributionofchargesproduces electricfield charges in motion current producesmagneticfield achangingmagneticfield electric field achangingelectric field magnetic field the fieldsarecontinuouslyrecreatedthroughem induction both fieldscan transportenergy a e fieldenergyused in electrical circuits. Properties of em waves nsinusoidalwavetravellingw frequency f awarelength a. Emwavestravel w different speeds in other media thehigherdensityofamedium theslower thespeedofpropagation ateverypointof an em wave e field and b field are related by. V xf so c ah af traverse e exampleoflongitudinal wave soundwave. Energyofemwaves if apowersourceemitsuniformlyinalldirectionsthe wave intensityat adistance r powerdensity pokey surfaceareaofasphere 4tr. 1 47 2 theintensityofa emwave dependson the amplitudesof the e b fields. Wavelength and wave nummbber wavelength a thedistancefromonewavecresttothenext unit. Wa wavenumber k k 25 unit m i or cm l mornin. E hf because c a t af and f c a. Polarization oscillationdirection whenlightis polarizedthismeansthatit"sonlyoscillatinginonedirection linearlypolarized ingenerallightisunpolarizedbutonceitpassesthrough a polarizerit"slinearlypolarized. Whatislight lightisapartofanemwave c 3. 108m sina vacuum wavefront vs ray distancetravelledbylight cot all lightfrom the source reaches the same distance thisplanecreated wavefront.
