A C B I D G H F E J      λ   λ           !"#$%&'(&)*+,,+$%)$%- * ./01/23  4)56123 λ 47&8)90:       λ λ   = = =     3#;<4 6 ** =>?1@ABAA"CDEA"=FG11AD=/"EHF/1ID=/@/ 2      ω π ϕ λ   ∆ = =     3#;J4   ϕ π ∆ =   !"#$%&'() [ ]   λ ⇒ = "*  ∈ 3#;K4  + , ϕ π ∆ = +  !"#$%-&()  ( )         λ λ     ⇒ = + = +  ÷       "*  ∈ 3#;#4  + ,   π ϕ ∆ = +  !"#$%".()  ( )      /    λ λ     ⇒ = + = +  ÷       "*  ∈ 3#;L4 *** /2/"CDEA"=MF11N2+D=/">GE < GE 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  *!",(-+ '       π π ϕ λ π π ϕ λ    = + +  ÷         = + −  ÷     os os F +  + 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   [&? O;N/ L*\9?(\9!L*:LP>%0 +02* !?Z]^ \9<L1? X;Z_L*+,2L*`WL/ (aW03<L02* !LV:L?Y/0/,<)02* W[%^#Q(aW[&? * *+,,+$%   &PQ YZ/[1B"CD12"=1\1">G"//\11]A+5G^"@> /_`/.+M5>GD/"CD; YZ/[1B"CD12"=1\1/C>G^"@>"U/`/.+M5>GD/ "CDMaDb8c6B@>1\1" YdV11BAAeAAP/2>/f@AagA612; • Giao thoa – Điều kiện đ có giao thoa:  Hb=[9+T)9+W,KcL02 **#[9+&=!=:?  de>9P]<%/)9+?J/ M1Y*>+ TfW[_? <; ANEA"=1I@A3h//\11]AAN+M5>G EhEA"=1\1"4 012(&I"#G$%&' () [ ]  $+  ,  $+  ,  g        ω π = = = JK3 !&7&!%;$1   "= 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    G   λ  λ  3;LG*)      $+  , g "       π π λ →   ⇒ = −     A4 /2/ij@/"CDFEAN2+G5//6       $ + , $   + , "  " g "             π π π λ λ → →     ⇒ = + = − − +          +/M, 4 5"=1]A2/ij@/F        ∆ = = −     F + +; 1 +; 1 3 E E 4 ϕ π λ +/D, 14 =>?1@A1]AA2/"CDF       3 E E 4 3 E E 4  ω π ϕ λ   ∆ = − = −     6   ∈ 3#;k4   &PQ CDEA"=1\1"+ DAb HJ+       ∆ = − =     3 E E 4 8 π ϕ π λ  [ ]   ⇒ − =E E 8 λ 6   ∈ 3#;<l4 ⇒ Tại những đim này hai dao đng thành phn cùng pha và biên đ dao đng của sóng tổng hợp cực đại.( h@>/C?a`/>/c) CDEA"=1\1/C+ D Hl         ∆ = − = +     3 E E 4 3 8 4 π ϕ π λ         ⇒ − = + = +E E 3 8 4 3 8 4 λ λ 6   ∈ 3#;<<4 ⇒ Tại những đim này hai dao đng thành phn ngược pha và biên đ dao đng của sóng tổng hợp cực tiu.( h@>/C?a`/"U//c). ∗ h"CDEA"=/=1"//\1Tg:L*%"=1\1"V 1\1"//mDQ%8Hl ⇒ A=!0RE'  = ± ?A=!0R'  = ± [Ee'@X=!0RI' D = ± BZW=:XL2' ⇒ A=:0RE' 4N  = − ?A=:0R' N  = − − [Ee'@X=:0RI' MN D = − E4 Fn$op,q rs'q*t* DẠNG 1: G;$1&7&L !*=@=-=#  C  O3$%"*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 λ − = + O$)=#(@?N ε =#(@W((a G>?>G==7&/U1GD=/0@@@V/ ./WQ<J7 AK  B 4 ε = =# !%&R$%cực đạiBậc K= n B 4 bM ε = =# !%&R$%cực tiuBậc n + 1 DẠNG 3: G%=c&(&I&'* !?&'!%(;$1&7& L !*=@=-=#  C  J7&V;$1&7&$S& λ C""#T @@ B\2Z&.[&) ( ) ( )      ; E E ; E E 3 4    − ∆ = − = ∗     ω π ϕ λ 7 $%&'( d ϕ π ∆ = "#$ 3 4∗ ⇒ 3=-&@! 7$%-&( ( )  d ϕ π ∆ = + "#$ 3 4∗ ⇒ 3=-&@! 7$%".( ( )    d π ϕ ∆ = + "#$ 3 4∗ ⇒ 3=-&@! &PQ) 7dV11BAAe3"CDEA"=1\1"4AAP/3"CDEA"=1\1/C42>/f@ AagA612  >  λ = DẠNG 4: J7&V"V]"#> !$%&P&3?$3G+d*"#G=#, @@ B0e=# !$%&P&3?$3G"#&7&CG=@=-8$3  C  O&)        E E d +5 d E 3 4 E E +5 λ λ + =    ⇒ = + ∗    + =    Bf$  4 E +5≤ ≤ 6-("* 3 4∗ \) +5 +5 d λ λ   − ≤ ≤      3 4∗ ∗ "* d u∈   &PQ) • ^7& !$%&P&3?$3G+]&1 !"#G"#G=# !$%&P&3, &]=#7g&7&7V6h!R&.[& 3 4∗ ∗ • dV]&7& !$%&P&3i7&V9j&.[& 3 4∗ DẠNG 5: J7&V"V]"#> !$%&P& ?$3G+d*"#G=#, @@ B0e=# !$%&P& ?$3G"#&7&CG=@=-8$3  C  O&)           / E E d +5 E 3 d 4 3 4 E E +5 λ λ    + = +     ÷ ⇒ = + + ∗         + =  Bf$  4 E +5≤ ≤ 6-("* 3 4∗ \)     +5 +5 d λ λ   − − ≤ ≤ −      3 4∗ ∗ "* d u∈   &PQ) • ^7& !$%&P& ?$3G&]=#7g&7&7V6h!R&.[& 3 4∗ ∗ • dV]&7& !$%&P& i7&V9j&.[& 3 4∗ • &2/CEI1/U1A311J4"CVE#GEL &1Jfb1"v0"CDEA"=1\1"G1\1/C/"+5 aR+PY+Xh!' G>?>G==7&/U1GD=/0@@@V/ ./WQ<J7 A#    = +     g  i λ "2@9#"*   (∈ ,NJ@9/.@@m GUY:L*1\1"2!`g'#WYj& [ ]  ; + 3fwHl/A"CD+M5>GA"CDEA"=1\1"4 SUY:L*1\1/C2!`g#WYk& [ ] [ ] 4 b   4 b M ; ; w M  <   + ≥   2n neáu X neáu &PQfb1"v0"CDEA"=1\1"G1\1/C/8V+5 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  <   + ≥   2n neáu X neáu J; AEA"=j1@A3h//\11]AAN+M5>GEhEA"=1\1/C4 +  , +  ,N ω π = =        "# +  , +  ,N ω π π π = + = + g       A4 5"=1]A2/ij@        + A;  3E E 4 A; 1 3 E E 4 π π π λ λ     = − = − +         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 = =        "# +  , +  ,N   π π ω π = + = + g       A4 5"=1]A2/ij@       / / + A;  3E E 4 A; 1 3 E E 4 π π π π λ λ       = − − = − +             3#;<L4 4 CDEA"=1\1"   / E E 8 λ λ   − = +     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 $% - H\L=#c-$$8*"#(1i3?&'!%"W#3$# G>?>G==7&/U1GD=/0@@@V/ ./WQ<J7 AL 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 λ G  %@&>V  λ  λ G  %@9V;]kl9*& m@9V;]k9*& @nko9*&  8"V]&>V&9?%$%&P&3+9Z,"#8 !;.$%+p, _q) B\L&r-& =#&&7&p"#&7&9Z10"v/8A B0*310"v⇒ P/2 B0*3/\E⇒ 5e2 BN(7⇒ -&&$@p=#P/2 BG%9Z/+"*=#9?%$%&I, <; A"9Em10"v) A4 Điều kiện về chiều dài  g= của dây có sóng dừng)     ;  +5 >   ; :   = = = =     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,  / λ = D "*m = 1, 3, 5, 7… 4 S nt và s bụng sóng) B\>9?X B\>9ZX>pXB Mt s đim cn ch  khi gii ton: <; .:67/><V:</l l=S L*9+TV? J; ./1Y3T9X/f,1WY3#=&07? K; Ulm]<n/Y/%*02T/+X6h?Z,1Y /n9071Y/hf%!S -2? G>?>G==7&/U1GD=/0@@@V/ ./WQ<J7 AO m@&>V .  3#;<J4 4 CDEA"=11"        E E 3 8 4 3 8 4 λ λ   − = + = +     3#;<K4 14 CDEA"=11/C [ ]   E E 8 λ − = 3#;< #4 E4 $0"CDEA"=11"G11/Cj1b1"vj1>6111/U18ANEA "=1I@A K;. A"9Em10"v) A4 Điều kiện về chiều dài  g= của dây có sóng dừng)     ;  +5 >   ; :   = = = =     λ "*   (∈ 3#;<L4 4 S nt và s bụng sóng)  e:Lf)>p>9Z!%$"V B>9ZX>9X B>pXB . ?$3G"#&7&CG=@= - 8$3  C  O&)           / E E d +5 E 3 d 4 3 4 E E +5 λ λ    + = +     ÷ ⇒ = + + ∗         + =  Bf$  4 E +5≤ ≤ 6 -( "* 3 4 ) 