A
C
B
I
D
G
H
F
E
J





λ


λ



 





!"#$%&'(&)*+,,+$%)$%-
* ./01/23


∆ =
  !"#$%&'()
[ ]
 
λ
⇒ =
"*
 ∈
3#;K4

+ ,
ϕ π
∆ = +
 !"#$%-&()

( )

 
 
  
λ
λ
 
 
⇒ = + = +
 ÷
 
 
 
"*

J

012(3&3)
[ ]
4 4
 $+  ,  
ω ϕ
= +
⇒
 !"#$ %&'

4 4
 
 $+  ,  $+  ,
"

       
π
ω ϕ ϕ π ϕ
λ
 
= + − ∆ = + −
 
 
3#;O4
&PQ()*!+ '
+
H+;13R/ST
+
4

 +
E
 +;1 : ;/
E
 +;1 : ;/
Mt s đim cn ch  khi gii ton:
G>?>G==7&/U1GD=/0@@@V/ ./WQ<J7 A<
56$1&7&8 !&'(
9:;<=#!%>?=@9*&
56$1&7&8 !-&(
9:;<=#!%>=A29*&

&$
B4CDE
FCE

G

<;./+01/+ 2/345#6789/&:
;</=>+?
@A'BCDE,F5CGH,I5
J;J:</=>+K:L2M+,2L<2L@9"=>?1@A
BAAEA"=;?
K;NO P*Q/+16RS

:4@*T?
#;UVP9/LWRS,W9XW?
L;@RY+7*0<S>!TLW?Z/
LW/,RY-[#1YT 



 "=
C&7&G!%;$1

 g"=
3;L*)


 
 $+  ,
 "

    
π
π
λ
→
 
⇒ = −
 
 
G>?>G==7&/U1GD=/0@@@V/ ./WQ<J7 AJ
 G


λ
G




λ λ
→ →
 
 
⇒ = + = − − +
 
 
 
 

+/M,
4 5"=1]A2/ij@/F
 
 

 
∆
= = −
 
 
F
+ +; 1 +; 1 3 E E 4
ϕ π
λ
+/D,
14 =>?1@A1]AA2/"CDF

   

3 E E 4 3 E E 4

⇒ − =E E 8
λ
6
 
∈
3#;<l4
⇒
Tại những đim này hai dao đng thành phn cùng pha và biên đ dao đng của sóng tổng hợp
cực đại.( h@>/C?a`/>/c)
CDEA"=1\1/C+
D
Hl 
 

 
 
∆ = − = +
 
 
3 E E 4 3 8 4
π
ϕ π
λ

 

 
 
⇒ − = + = +E E 3 8 4 3 8 4
λ


O3$%"*9?% &P&308
"*QP&&IG&R&P&3;7&O!"$S&T+9#U&$!%$3=-,
@@
SJ7&V9W&6&IR&P&33)
d
XB
BY(Z&.[&&$ !$%&P&3)

 

E E d d ;; d
:
λ
− = = =
B\3=-&@!)"$S&T
DẠNG 2: G;$1&7&L !*=@=-=#

C

J7&V]&:&I !$%
^$9
λ
$S&""#T
@@
B_W(`>)
 
E E

ε

 
 

; E E
; E E 3 4

 
−
∆ = − = ∗
 
 
ω
π
ϕ
λ
7 $%&'(
d
ϕ π
∆ =
"#$
3 4∗
⇒
3=-&@!
7$%-&(
( )
 d
ϕ π
∆ = +
"#$
3 4∗

 
 
E E d
+5 d
E 3 4
E E +5
λ
λ
+ =

 
⇒ = + ∗

 
+ =
 

Bf$

4 E +5≤ ≤
6-("*
3 4∗
\)
+5 +5
d
λ λ
 
− ≤ ≤
 
 


 
+ = +

 
 ÷
⇒ = + + ∗
 

 
 

+ =

Bf$

4 E +5≤ ≤
6-("*
3 4∗
\)
 
 
+5 +5
d
λ λ
 
− − ≤ ≤ −
 
 


[ ]
4 b
  4 b
M ;
; w M

<


+ ≥


2n neáu X
neáu
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B$0EA"=1\1")
 J;)<3fwHl4
 J;S<3fw
≠
l4
S$0"CDEA"=1\1/C/\/
[ ]
[ ]
4 b
  4 b
M ;
; w M

<


 
 
3#;<J4
4 CDEA"=1\1"
 

 
 
E E 3 8 4 3 8 4
λ
λ
 
− = + = +
 
 
3#;<K4
14 CDEA"=1\1/C
[ ]
 
E E 8
λ
− =
3#;<#4
E4 $0"CDEA"=1\1"G1\1/Cj1b1"vj1>6111/U18ANEA
"=1I@A
K; AEA"=@A
+  , +  ,N
ω π
= =


 
− = +
 
 
3#;<K4
14 CDEA"=1\1/C
( )
 
 
 /
E E 8
λ λ
 
− = + +
 
 
3#;<O4
E4 $0"CDEA"1\1"a60"CDEA"=1\1/C
 
/ /
+5 +5
d− − ≤ ≤ −
λ λ
3#;<X4
$%
-
H\L=#c-$$8*"#(1i3?&'!%"W#3$#
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YdV11BAAex1AP/>/f@AagA612;
YdV11BAD=/eGD=/P/>/f@Aa<y#612;

= = = =
 
 
λ
"*

 (∈
3#;<L4
4 S nt và s bụng sóng)
 e:Lf)\>p>9Z!%$"V
B\>9ZX>9X
B\>pXB
 e:L07)\>9Z>p!%$"V
B\>9?XF
B\>9ZXB
B\>pX
 F=/"910"vD=/"9/\E\>9ZX>p
A4 Điều kiện về chiều dài
 g
=
của dây có sóng dừng)
( )
 
/  /
λ λ λ
= = + = ++5 >  
"*

 (∈
+/s,