Physics 721 Homework 11: Electromagnetic Waves and Energy Density, Assignments of Physics

Download Physics 721 Homework 11: Electromagnetic Waves and Energy Density and more Assignments Physics in PDF only on Docsity! Physics 721 Homework 11 Assigned: Mon. 4/04/05 Due: Mon. 4/11/05 1. Jackson 7.2 2. Jackson 7.4 3. Jackson 7.13 4. The electric and magnetic fields in vacuum at 
 are 
   
    where  
  for a given constant ! . a) Find the electromagnetic energy density, momentum density, and their ratio. b) Show that at #"$ , there are two wavepackets travelling in the direction  and %  . For what ratio &'( ' is there just one wavepacket? How much of the initial energyof the field is carried in the  and %  direction? c) What are the group velocities of the two wave packets? What are their phase veloc- ities? Should their magnitudes be different? 1