tailieunhanh - Physics exercises_solution: Chapter 32

Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 32 | x d X 108 m _ a t - ----------------- s. c x 108 ms b Light travel time is o z n z x 365 days 24 hours 3600 s _ 1Z 8 years years ------- ------------- --------- x 108 s 1 year 1 day 1 hour d ct x 108 ms x 108 s x 1016 m x 1013 km. d cAt x 108 ms x 10 7 s 180 m. B B . cos kz - at j B . cos 2tf -t11 j i i c j j z B z t x 10 4 T cos 2 x 1014Hz 8 I I x 108 m s ai i t lJ J7 B z t x 10-4 T cos x 107 m-1 z - x 1015 rad s t j. E z t By z t j x ck E z t x 105 v m cos x 107 m-1 z - x 1015 rad s t i. a f - 100 x 10 ms x 1 Hz. X x 10-7 m b B J max E 2 0 x 10-3Vm x 10-12 T. c x 108 ms c The electric field is in the x -direction and the wave is propagating in the -z-direction. So the magnetic field is in the -y-direction since S œ E x B. Thus A z E z t Emax cos kz at i Emax c s 2nf t I I I Ic 77 E z t x 10-3 V m cos 2n x 1014 Hz t . . I I x 108 msJJ E z t x 10-3 v m cos x 107 m-1 z x 1015 rad s t i. i And B z t E z t j - x 10 12 T cos x 107 m 1 z x 1015rad s t j. c a y direction. nr 2 . a 2nj -- X X b 2nc _ 2k x 108 m s a x 1O12 rad s x 10 4 m. c Since the electric field is in the - z -direction and the wave is propagating in the y -direction then the magnetic field is in the - x -direction S œ E x B . So B y t y t i sin ky - cot i sin y - cot i c c c c - . f x 1O5V m . f x 1O12 rad s 1aU A B y t -1-----z 4- I sin I --------- y - x 1012 rad s t i 1 x IO8ms x 108 m s B y t - x 1O-3 T sin x 1O3 m y- x 1O12 rad s t i. a - x direction. 2n 2n f kc 1O4 rad m x 1O8 m s in11TT b k f ---------------------- 6 59 x 1O11 Hz. c Since the magnetic field is in the y -direction and the wave is propagating in the - x -direction then the electric field is in the z -direction S œ E x B . So E x t cB x t k cBO sin kx 2k f k E x t c