7
. 1 c =A+ B 2

1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

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Page 1: 1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

.

1

c= A +

B

位2

Page 2: 1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

.

A

810B

t1A1f

1x

饾湅饾憮1饾憽sin21t =A1sinw1=A1X

2A2f2x

饾湅饾憮2饾憽sin22t =A2sinw2=A2X

xt

2+x1X= x

t2sinw2t + A1sinw1A

2+A1A=A

t2t+A sinw1X = A sinw

饾懃 = 2饾惔 饾憪饾憸饾憼 (饾懁2鈭掟潙1

2) 饾憽 饾憼饾憱饾憶 (

饾懁2鈭掟潙1

2) 饾憽

1,w2w10Hz (

Page 3: 1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

.

饾憮2 鈭 饾憮1 = 鈭嗮潙 鈮 10饾惢饾懅

鈭 饾懃 = 饾惖 饾憼饾憱饾憶 (饾懁2鈭掟潙1

2) 饾憽

饾惖 = 2饾惔 饾憪饾憸饾憼 (饾懁2鈭掟潙1

2) 饾憽

B

饾憼饾憱饾憶 (饾懁2+饾懁1

2)

12饾惔鈮 饾惖 鈮

2A饾憪饾憸饾憼 (饾懁2鈭掟潙1

2) 饾憽 = 卤1

N0,1,2,鈥

T 蟿 =

1

饾憮2鈭掟潙1=

1

鈭唂

f鈭

B饾憪饾憸饾憼 (饾懁2鈭掟潙1

2) 饾憽 = 0

(100cm(101cm

饾憮 = 饾懀

位=

饾懀

100

饾憮 = 饾懀

位=

饾懀

101

Page 4: 1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

.

3 =

18

6

饾憮2 鈭 饾憮1 = 饾懀

100鈭

饾懀

101= 3

V=303m/sec

1-

味 = asin(饾懁饾憽 鈭 饾憳饾懃) , 饾懁 = 饾憳饾惗 , 饾憳 =2饾湅

饾渾

饾渷 = 饾憥饾憼饾憱饾憶2饾湅

饾渾(饾憪饾憽 鈭 饾懃)

C

饾憿 =饾憫饾渷

饾憫饾憽=

2饾湅饾憥饾憪

饾渾 饾憪饾憸饾憼

2饾湅

饾渾 (饾憪饾憽 鈭 饾懃)

uc

u

Page 5: 1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

.

2-

. 饾憠饾憹鈩 = 饾懁

饾憳 = 饾渾饾憮

x-ut

x2f(x) = x 2ut)-ut) = (x-f (x

xtx,t

4

p

x-ut=constant

饾憫饾懃

dt鈭 u = 0 鈬

dx

dt= u

dx

dtphase velocity

爻乇毓丞 丕賱賲噩賲賵毓丞 -3

Vg = 鈭倃/鈭俴

Page 6: 1 =A+ B c 位2聽路 A B 810 f 1 A 1 t x 1 X 1 =A 1 sinw 1 t =A 1 sin2 饾湅饾憮1 x 2 f 2 A 2 X 2 =A 2 sinw 2 t =A 2 sin2 饾湅饾憮2 t x X= x 1 +x 2 A 1 sinw 1 t + A 2 sinw 2 t A=A 1 +A

.

饾憠p =w

k 鈬 w = 饾懀饾憹饾憳

dw = 饾懀饾憹. 饾憫饾憳 + 饾憳. 饾憫饾懀饾憹

饾懀饾憯 =饾憫饾懁

饾憫饾憳=

饾懀饾憹.饾憫饾憳+饾憳.饾憫饾懀饾憹

饾憫饾憳= 饾懀饾憹 + 饾憳

饾憫饾懀饾憹

饾憫饾憳

噩爻賷賷 -丕夭丿賵丕噩賷丞 賲賵噩丞

丕賱鬲丿丕禺賱兀胤賵丕乇賲賵噩丕鬲 噩賷亘賷丞

賴丿丕賲鬲丿丕禺賱丕

丕賱丿丕賱丞 丕賱賲賵噩賷丞亘賰賲賷丞 丨乇賰丞

c

1-sec