波的傳播規(guī)律

1、14710131受干擾，開(kāi)始向上振動(dòng)受干擾，開(kāi)始向上振動(dòng)0tvy2xy4Tt 4開(kāi)始開(kāi)始1471013vxyy141xy1471013v開(kāi)始開(kāi)始2Tt y471v1471013xy開(kāi)始開(kāi)始43Tt v1471013xy開(kāi)始開(kāi)始Tt y71041y1013174討論：討論：(3)依靠質(zhì)元間的彈性力依靠質(zhì)元間的彈性力, ,“上游上游”質(zhì)元依次帶質(zhì)元依次帶動(dòng)動(dòng)“下游下游”質(zhì)元質(zhì)元振動(dòng)振動(dòng)(2)波是振動(dòng)狀態(tài)的傳播，各波是振動(dòng)狀態(tài)的傳播，各在各自平衡在各自平衡位置附近振動(dòng)位置附近振動(dòng)(1)1振動(dòng)振動(dòng)1個(gè)周期后，其初相位傳到個(gè)周期后，其初相位傳到1313質(zhì)元質(zhì)元相位滯后于相位滯后于1質(zhì)元質(zhì)元2 14710

2、13xy質(zhì)元質(zhì)元不不傳播傳播 質(zhì)元振動(dòng)方向與質(zhì)元振動(dòng)方向與波傳播方向垂直波傳播方向垂直質(zhì)元振動(dòng)方向與質(zhì)元振動(dòng)方向與波傳播方向相同波傳播方向相同四、四、波速波速F波速波速：振動(dòng)狀態(tài)傳播的速度：振動(dòng)狀態(tài)傳播的速度F波速由介質(zhì)的波速由介質(zhì)的彈性模量彈性模量和和密度密度( ( ) )決定決定Gu Yu fflSffllBu Tu T ：繩中的張力繩中的張力 ：?jiǎn)挝婚L(zhǎng)度的質(zhì)量單位長(zhǎng)度的質(zhì)量0VVffff波射線波射線波射線波射線)cos(0tAyux)(),(0uxtytxy)(cosuxtA平面諧波的波動(dòng)方程平面諧波的波動(dòng)方程xyOP)()(utuxttuxt)(uxxtt),(),(ttxxytxy經(jīng)

3、經(jīng) 波形沿波線傳播了波形沿波線傳播了 x的距離的距離t)(cos),(uxtAtxyxx0ytttABx AAB )(uxt)(uxttA Attt)(ty)(cosuxtAyuxtyO) cos(tAy) (cosuxtAy)(xyt) cos(uxAyxyO22TTu)(cosuxtAyuxtAycosxTtA2cosxtA2cos22tya)(cos2uxtA)(cos2222uxtAuxy222221tyuxy)(cosuxtAy222221tyuxy22002tEE22002tBB001cm/s109979. 28 米) 39cos(1062ty)(cosuxtAym1062A93u

4、m3)2(9cos1062xty23629sm2m)69cos(1062ty) 39cos(1062tym)1832cos(1062xy1)1832cos(xkx218322, 1, 0)3612(kkxm3)2(9cos1062xtymxmyOu2 . 02 . 04 . 0ab)cos(tAym2 . 0Am4 . 02u24 . 008. 02520y0v2mxmy0um)252cos(2 . 0tym2)08. 0(52cos2 . 0 xtyABux)10(2cos2xty)1005. 0(2cos2tyB)1002cos(2t100)10(2cos2xtytyvBBdd)1002s

5、in(4t4maxBvtyv)(sinuxtA)(cosuxtAy221vmWk2)(21vV)(sin21222uxtAVkpWW pkWWW)(sin)(222uxtAV)(sinuxtAv)(cosuxtAy)(sin)(222uxtAVEVWw)(sin222uxtATtwTw0d12221A)(sin)(222uxtAVWSuwp SuuSPI 2221Auuw2221Az2221Aw uz2AI 2221AzI2ItutuA1A2ABC A iii iCAAA2CAAACA2CAAACA20290iCAAiACA ii A1A2ABCi1u2uABiACCAsin2tu 1sinA

6、CAAtu 22121sinsinnuui21uu )cos(11010tAy)cos(22020tAy1S2SP1r2r)2cos(1111rtAy)2cos(2222rtAy21yyy)cos(tA)2cos(21212212221rrAAAAA)2cos()2cos()2sin()2sin(tan222111222111rArArArA 12122rr 2AI cos22121IIIII空間各點(diǎn)的強(qiáng)度與空間各點(diǎn)的強(qiáng)度與 有關(guān)有關(guān)：隨位置變化，但穩(wěn)定隨位置變化，但穩(wěn)定cos2212221AAAAA12122rr 2, 1, 02kk21AAA2, 1, 0) 12(kk 21AAA2121

7、2IIIII21212IIIIImaxAminAcos2212221AAAAAcos22121IIIII21k212k, 2, 1, 0k12rr maxAA 12rr minAA 12122rr x01x2x1S2S) 12(2)(21112kxxd) 12()2(2112kxd) 32()2(2212kxdx01x2x1S2S2)(412 xx)(212xx )912(2m6)2(2) 32(212xdk)52(k12) 12()2(2112kxd) 32()2(2212kxduu0t0 x4Tt 2Tt 0 x0 xuu0t0 x0 x0 x)(cos1uxtAy)(cos2uxtAy2

8、1yyytuxAcos)cos(2uxAcos2)(uxttuxAycos)cos(20 xukx 2k2kkkxxx121cosux, 2, 1, 0kkux0cosux2, 1, 022kkx4) 12(kx20 xtuxAycos)cos(2 uz uz1u2u222u11u122u1u22u11u12tAy2cos0uxdOx)(2cosudtAyd)(2cosudtAyduxd )(2cosuxdudtAy)2(2cosxdtAuxdOx波疏波密0 x入射波入射波反射波反射波xy0)(cos01uxtAy)(cosuxtAy)(cos2uxtAy)()(00uxtuxtux02ux02)2(cos02uxuxtAy)(cos02uxtAy波疏波密0 x入射波入射波反射波反射波xyOxl)(cos02uluxtAy)(cos00uxxuxtA)2(cos0uxuxtAsbbvubvu bvu uvub)1 (uvb)1 (uvb低于波源頻率低于波源頻率 ssbbsvTvsTvsTvuTsTvus)( uTvuus)( svuusvuubvu Tvus)(bvuTvuvusb)( sbvuvusbvuvuvRSs1svuvu212bsvuvu) 1(bsvvu242 . 022 . 0340Hz3398可聞聲波可聞聲波)(cos),(uxtAtxyVxSVySVVVa