Unformatted text preview: 94. (a) The wave is traveling in the −y direction (see §175 for the signiﬁcance of the relative sign between
the spatial and temporal arguments of the wave function).
(b) Figure 345 may help in visualizing this. The direction of propagation (along the y axis) is perpendicular to B (presumably along the x axis, since the problem gives Bx and no other component)
and both are perpendicular to E (which determines the axis of polarization). Thus, the wave is
z polarized.
(c) Since the magnetic ﬁeld amplitude is Bm = 4.00 µT, then (by Eq. 345) Em = 1199 V/m. Dividing
√
by 2 yields Erms = 848 V/m. Then, Eq. 3426 gives
I= 1
2
E 2 = 1.91 × 103 W/m .
cµ0 rms (d) Since kc = ω (equivalent to c = f λ), we have
k= 2.00 × 1015
= 6.67 × 106 m−1 .
c Summarizing the information gathered so far, we have (with SI units understood)
Ez = 1199 sin 6.67 × 106 y + 2.00 × 1015 t . (e) and (f) Since λ = 2π/k = 942 nm, we see that this is infrared light. ...
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This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.
 Fall '08
 SPRUNGER
 Physics

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