- . , . , . .
.
p
(. 3.1). (. 3.1, , ). , , . . , .
, (. 3.1, ). , , . . .
, , , .
. 3.1.
u
(3.1)
. r ; ; N . . N E , .
. , 1, 7 ( ). , . , , .
, .
, t. .
, . . , .
, , .
, .. (. 3.2)
|
|
. 3.2.
l , . - p, p pp p p, ..
l = u × = u /n = 2p u / w, (3.2)
; w (w = 2pn); u .
p
. 3.3, .
. 3.3
t , , x = cos(w t), x .
t , t x = cos w (t -t), t = /u.
x (, t) = cos w (t - /u) = cos (w t -w × /u). (3.3)
k: (3.4)
(3.4) , ,
x ,t = cos (w t - k + j0), (3.5)
; j0 , t; (w t - k + j0) .
, , ,
x ,t = cos (w t + k + j0).
x t , .
p (3.3, 3.5) p t , ( ), u (. 3.4). x (, ) , x = 0. l , .
. 3.4
p t + D t p ( . 3.5) p p p ppp .
x, p , p x (p. 3. 6). . 3.4 3.6. , : x () ; x(t) .
(3.5) x(t) = cos (w t + j) j = - kx + j0., , . Dj, , 1 2 , ( )
Dj = k (x 2 - x 1) = k D x. (3.6)
|
|
1. 340 /. 170 , 0,3 . , , .
. l = u × = = u /n, l= 340/170 = 2 .
x (, t) = = cos(w t - k) w = 2pn = 2p∙170 = =340p -1, k = 2p/l = =2p/2 = p -1. x (, t) = 3×10-4 cos (340p t - p ) (. 3.7).
2. x (, t) = 0,1cos (p t /2 -p x /20) . : 1) ; 2) 1 2, , , 20 60 ; 3) 1
. : k = 2p/l = p/20 -1; 2/l =1/20; l = 40 . (3.6):
Dj = p(60 - 20) / 20 = 2p.
1,
x (t) = 0,1cos (p t /2 - p) .
(. 3.8) , : = 2p/w, .. = 2p/(p/2) = 4 .