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Unformatted text preview: Chapter 33 1. In air, light travels at roughly c = 3.0 10 8 m/s. Therefore, for t = 1.0 ns, we have a distance of d ct ( . . 30 10 0 30 8 9 m / s)(1.0 10 s) m. 2. (a) From Fig. 332 we find the smaller wavelength in question to be about 515 nm, (b) and the larger wavelength to be approximately 610 nm. (c) From Fig. 332 the wavelength at which the eye is most sensitive is about 555 nm. (d) Using the result in (c), we have 8 14 3.00 10 m/s 5.41 10 Hz 555 nm c f ﾴ ﾴ l . (e) The period is (5.41 10 14 Hz) –1 = 1.85 10 –15 s. 3. (a) The frequency of the radiation is f c l 30 10 10 10 64 10 4 7 10 8 5 6 3 . ( . )( . . m / s m) Hz. (b) The period of the radiation is T f 1 1 4 7 10 212 3 32 3 . min Hz s s. 4. Since l l , we find f is equal to l c c l l F H G I K J 2 8 9 9 9 30 10 632 8 10 7 49 10 ( . ( . . m / s)(0.0100 10 m) m) Hz. 2 5. If f is the frequency and l is the wavelength of an electromagnetic wave, then f l = c . The frequency is the same as the frequency of oscillation of the current in the LC circuit of the generator. That is, f LC 1 2 / , where C is the capacitance and L is the inductance. Thus 1311 CHAPTER 33 l 2 LC c . The solution for L is L Cc l 2 2 2 9 2 2 12 8 2 21 4 550 10 4 17 10 2 998 10 500 10 m F m / s H. c h c hc h . . This is exceedingly small. 6. The emitted wavelength is ( ) ( ) ( ) 8 6 12 2 2 2.998 10 m/s 0.253 10 H 25.0 10 F 4.74m. c c LC f l ﾴ ﾴ ﾴ 7. The amplitude of the magnetic field in the wave is B E c m m 320 10 2 998 10 107 10 4 8 12 . . . V / m m / s T. 8. (a) The amplitude of the magnetic field is 9 9 8 2.0V/m 6.67 10 T 6.7 10 T. 2.998 10 m/s m m E B c ﾴ ﾴ ﾴ ﾴ . (b) Since the wave E r oscillates in the z direction and travels in the x direction, we have B x = B z = 0. So, the oscillation of the magnetic field is parallel to the y axis. (c) The direction (+ x ) of the electromagnetic wave propagation is determined by E B ﾴ r r . If the electric field points in + z , then the magnetic field must point in the – y direction. With SI units understood, we may write ( ) ( ) 15 15 8 9 15 2.0cos 10 / cos 10 3.0 10 6.7 10 cos 10 y m t x c x B B t c x t c ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ ﾴ 9. If P is the power and t is the time interval of one pulse, then the energy in a pulse is 32 E P t 100 10 10 10 10 10 12 9 5 W s J....
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This note was uploaded on 04/19/2008 for the course PHYS 1100, 1200 taught by Professor Many during the Fall '08 term at Rensselaer Polytechnic Institute.
 Fall '08
 Many
 Physics, Light

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