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Gan nhau nhat tren cung mpt phuang truyen s6ng ma dao dpng tai hai diem do cung pha.. Tren cung mpt phuang truyen song ma dao dpng tai hai diem do cimgpha... Trong khoang thai gian 2 s

Trang 1

CHltawe 1: DAD nOWB CB m VJT I t n - TtM TAT Lt THUYfT VA BAl TAP TRAC MHlgM - Ti

Trang 2

CIHMRG1:DMB(IIGCI(HQC WAT It« - JtU TAT I Y THBTfT WA BAl TAP THAC • B H I C M - T A P I

Cau 46: Chieu dai 16 xo ti I5 nghich voi dp cung, cat bat 16 xo mpt

nura =^ do cung tSng gdp doi => chu ki giam ^/2

Cau61: t = 0,Xo = 0,i;o < 0 ; ^ = 1,5

-» At = 1,5T -> CO 4 Idn qua vjtrix = -2cm

t = 0

-4 - 2 0 +4 Chii y: trong mpt chu ki c6 hai Ian vat di qua vi trf x = 2cm

Cau 62: = Wt =^ \x\ ^-^ A = 6cm; max = 10 rad/s -> 7 = 0,628 s

^ mi = 2505,m2 = 1605f Cau 65: M = 0-* IQ = Imax - A = 36cm

Trang 3

CHlAfNG l:DA00QNGCdH9C tfAT lY 12 - T U M T A T LY THUYgj V A B A I T A P T B A C N G H I E M - TiJP 1

W A T lY 12 - TdM T A T lY THUYfT W A B A I T A P T B A C HGHigM - T A P 1 CHtfflHB 1: DAO njlllG M Hn

C a u 83: Aco = lOO/r co = lOn rad

-^T2-Ti = -0,01s < 0: dao dong nhanh 0,01s

C a u 9 8 : J ="1 '1 "1 1^ = ^/IMT2 = yflM 100% = 20o/o

Trang 4

V A T LY I Z - T t M T A T It THBYfT W A BAI T A P TBAC WHIgM - TAf 1 CHlfini61:B*B0tll6CtfH9C

Cau 112: A(p =^ yA = yjAl + Aj = 5cm Cau 113: A = yjAl + A^ + 2i4i>42COS (<P2 - (Pi) = 9cm

Cau 114: Dap an A vd B sS khong chpn vi dao dpng 2 cung pha vol

dao dpng 1, khong thoa phucmg trinh dao dpng tong hgp Neu chgn C thi

khong thoa pha ban dau cua dao dgng tong hgp Dap dn D la phu hgp vi khi

hai dao dong ngu(/c pha, pha ban ddu cua dao dpng tSng hgrp ciing pha ban

ddu vai dao dgng thdnh phdn c6 bien dg Ian han

Trang 5

CHlfdNG 2: SdNG Cd

VAT LV 1? - TdM TAT li THUYgT VA BAl TAP TRAC NGHI|M - TAP 1

CHLTonVG 2

SONG CO

^ VAN BE 1; BINH NGHJA SONG CO

• Song ca hgc la nhung dao dpng car Ian truyen trong moi truong

vat chat theo thai gian

Phuomg trinh song: u = acos(6)t + q))

• Song ngang: Song c6 phtromg dao dong vuong gdc vai phuomg

truyin song

• Song dQc: Song c6 phuong dao dong trung voi phuomg truygn

song

Song CO khong truyen duac trong chan khong

Khi song truyen tir moi truong nay sang moi truomg khdc, tan so

song khong doL

• Bir6'c s6ng(A):

- QuSng duong song truyen dugc trong mpt chu ki

- Khoang each ngdn nhdt giiia 2 diem tren phuomg truyen

song ma dao dgng ciingpha

X = vT = J

Trong do: A: Buac song (m)

v: Toe do truyen song

Bai tap mau; Mgt nguon song dao dpng c6 phuomg trinh

u = 2 cos(160;rt) (u tinh bSng cm, t tinh bang giay) tao ra song c6 toe dp

Ian truyen trong khong khi v = 330m/s

a Xac dinh bien dp, chu ki, tan so

b Tinh budc song trong khong khi

c Trong 2s s6ng truySn dupe quSng du6mg b3ng bao nhieu Ian

bu6c s6ng

d S6ng tren truyen tir khong khi vao nu6c, biet v^n toe truyen s6ng trong nuae 1^ 1452 m/s, tinh bu6e song trong nu6c

DAT LY 12 TdM TAT lY THUYfT tfA BAI TAP TBAC llfiHIgM - TAP 1 CNIfdRG 2: SdNG Cd

Can 1: (De thi tot nghiep nam 2007) Phdt bieu n^o sau day \h dung khi

noi ve song ca hpc?

A Song am truyen dugc trong chan khong

B S6ng dpc 1^ song eo phuomg dao dpng vuong g6e voi phuomg

truygn song

C Song dpc la song eo phuong dao dpng trung vdi phuong truyen song

D Song ngang la song c6 phuomg dao dpng trung voi phuomg truySn song

Can 2: (De thi tot nghifp nam 2008) Khi noi ve song ca hpc, phat bieu

nao sau day la sai ?

A Song ca hpc la svr Ian truySn dao dpng ca hpc trong moi truong vat

chat

B Song ca hpc truyen dupe trong tat ck cdc moi trudng rSn, 16ng, khi

va chan khong

C S6ng am truyen trong khong khi 1^ song dpc

D Song ca hpc Ian truyen tren mat nu6e 1^ s6ng ngang

Cau 3: (De thi dai hpc nSm 2009) Buac s6ng 1^ kho^g edeh gifra hai

diem

A Tren cimg mpt phuang truyen s6ng dao dpng tai hai diem do

ngupre pha

B Gan nhau nhat tren cung mpt phuang truyen s6ng ma dao dpng tai

hai diem do cung pha

C Gan nhau nhat ma dao dpng t^ hai diem do cung pha

D Tren cung mpt phuang truyen song ma dao dpng tai hai diem do cimgpha

Trang 6

mm t SONG cd

V*T LY 12 - TiM TAT LY THUYfT VA BAI TAP TBAC NGHlf M - TilF 1

Cau 4: Goi A la buac song cua mpt song ca Khoang each giua hai diem

gan nhat tren phirorng truyen song dao dong eiing pha bang

A A/4 B A C A /2 D 2 A

Cau 5: Mpt son^ am Ian truySn trong khong khi voi van toe 350m/s, eo

buac song 7m Tan so song la

A 5000Hz B 2000Hz C 50Hz D 500Hz

Cau 6: Mot diem A tren mat nuac dao dpng voi tan s6 lOOHz Tren mat

nuac nguai ta do duge khoang each giua 7 gem 16i lien tikp la 3cm Khi do

van toe truyln song tren mat nuac la

A 50em/s B 50m/s C 5 cm/s D 0,5cm/s

Cau 7: Mpt nguai quan sat song tren mat h6 thhy khoang each giiJa hai

ngon song lien iiip bang 2m va c6 6 ngon song qua truae mat trong 8s

Van t6c truyen song tren mat nuae la

A 3,2m/s B l,25m/s C 2,5m/s D 3m/s

Cau 8: (De thi dai hQC nam 2010) Tai mot diem tren mat chat long c6 mot

nguon dao dpng vai tan s6 120 Hz, tao ra song 6n dinh tren mat chat long

Xet 5 ggn loi lien tiep tren mot phuang truySn song, a vS mot phia so voi

ngu6n, ggrn thu nhdt each gan thu nam 0,5 m T6C dp truyen song la

A 12 m/s B 15 m/s C 30 m/s D 25 m/s

Cau 9: Mpt song am c6 tan so xac dinh truyen trong khong khi va trong

nuac voi van t6c ISn lugrt la 330 m/s va 1452 m/s Khi song am do truyen tvr

khong khi vao nuac thi buac song cua no se

A giam 4,4 Ian B.giam41an C tang 4,4 Ian D tang 4 Ian

Cau 10: (De thi dai hqc nam 2007) Mpt nguon phdt song dao dpng

theo phuang trinh u = acos(207tt) (cm) vdi t tinh bang giay Trong

khoang thai gian 2 s, song n^y truyen di duge quSng duomg bang bao

nhieu ihn buac s6ng

• Qua trinh truyen song:

- Qua trinh truySn nang lugng

- Qua trinh truyen pha dao dong (trang thai dao dong)

- Cac phan tir vat chat dao dpng tai cho, khong bj Ian truyen

• D Q lech pha: /V<p = ^

- Cung pha: A<p = k2n

(2 diem gin nhau nhat tren phuang truyk song dao dpng cung

pha: Acp = 2n)

- Ngu"(/c pha: A<p = TT + k2n

(2 dilm gin nhau nhat tren phuang truyen song dao dong ngucc pha: A(p = TT)

- Vuong pha: A(p = | + kn

(2 diem gan nhau nhit tren phuang truyen song dao dong

vuorjg pha: A(p ~ ^)

X la khoang cdcx giua hai diim cdn tinh do l?ch pha (x vdX cung

don vi)

• Phu-ong trinh truyen s6ng

Song i, J /; n iheo phuang chieu Ox

- Phx( g (rinh song t^ ngu6n: uo = acos(6>t)

- Phj( ig tiinh s6ng tai M cdch O mot doan x do O truygn tai:

Trang 7

cHUifiG 2: SAMG ca »iT li n - TiM TAT tt TWYfT VA l A i ikr THAC •emCM-TAPi

B a i tap m a u ;

BM 1: Nguon song O dao dpng voi phuang trinh uo = 5 c o s ( 5 7 r t ) (cm) tao ra

song Ian truyen voi toe dp 24cm/s va gia su trong qua trinh truyen song bien

do song khong doi

a Tfnh dp lech pha cua mot diSm M tren phuomg truyen s6ng ngu6n

O biat OM = 3,2cm

b Tinh dp l?ch pha cua 2 diem P va Q tren phuang truyen song va c6

khoang each toi ngu6n O Ian lupt \k 2,4 den 3,6cm

c Wik phuang trinh song tai Q do nguon O truygn toi

c X = OP = 3,6cm: U Q = 5 cos (STA - ^ ) = 5 cos ^5ut - ~j

Bai 2: Song ca truyen trong mpt moi tnrang dpc theo tryc Ox voi

phuang trinh U = c o s ( 2 0 t - 4 x ) (cm) (x tinh bSng met, t tinh bSng giay)

Tinh van toe truyen song

Giai; u - cos(20t - 4x) <-> u = acos (a)t - ^ )

— _ = 4x = > A = - m -* V = A / = A — = - — = Sm/s

Bai tap 2

Cau 1: Phat biSu n^o sau day 1^ sai khi n6i ve qud trinh truyen s6ng:

A Qud trinh truySn song 1^ qud trinh truyen dao dpng trong m;

truomg dan hoi

B Qua trinh truyen song \k qud trinh truyen nSng lupng

C Qud trinh truyen s6ng la qua trinh truyen pha dao dpng,

D Qud trinh truyen s6ng la qua trinh truyln c&c phSn tii v§t chat

VAT li n - H M TAT i t TmiYgT wA B A I I A P T»AC twxtui - TAP I CHtfdllGZiSDNGCtf

Cau 2: Mpt song am c6 t i n so 450Hz Ian truyen vai van t6c 360 m/s trong

khong khi Dp lech pha giua hai diem each nhau 0,2m tren mpt phuang truyen song la

A ^(p=0,57u B A ^ = l , 5 ; r C A ^ = 2 , 5 ; r D l^cp=\5K

Cau 3: Song truyen t u O den M vai buac song 60cm Diem M each O

mpt doan 45cm thi tinh chit cua song tai M l a :

A M dao dpng nguprc pha voi O '

3;r

B M dao dpng cham pha hom O la ~

-hit

C M dao dpng nhanh pha han O la

D M dao dpng cung pha vai O

Cau 4: Mpt song c6 tan so 500Hz, t6c dp Ian truySn 300m/s Hai dilm gan

nhau nhat tren phuang truyen song phai each nhau gan nhat mpt khoang bao nhieu de giiia chung c6 dp lech pha bang y rad ?

A 0,1 m B 0,1 cm C 10 m D 1 cm

Cau 5: (De t h i cao dang nam 2009) Mpt song ca c6 chu k i 2 s truyen v6'

toe dp 1 m/s Khoang each giiia hai diem gan nhau nhat tren mpt phuang truyen ma tai do cac phan tu moi truang dao dpng nguac pha nhau la

A, 0,5m B 1,0m C.2,0m D 2,5 m

Cau 6 : (De thi dai hpc nSm 2009) Mpt song am truyen trong thep vai van

toe 5000m/s Neu dp l?ch cua song am do a hai diem gan nhau nhat each

nhau I m tren cung mpt phuang truy6n song la thi tan s6 cua song bang:

A 1000 Hz B 1250 Hz C 5000 Hz D 2500 Hz

Cau 7: Song truyen tren day voi van toe 4m/s T i n so cua song thay doi tu 22Hz d i n 26Hz D i l m M each nguon mpt doan 28cm luon dao dpng vuong pha voi ngu6n Buac song truySn tren day la:

A 160cm B 1,6cm C 16cm D 100cm

Trang 8

mm 2: sdNG cd VATLY 1 2 - T I > M T A T LY THUYfT VA BAI TAP TRAC H B H I E M - T A P I

C a u 8: (De thi dai hoc nam 2011) M p t song hinh sin truygn theo phuomg

Ox t u nguon O v a i tan s6 20 Hz, c6 toe dp trayen song nkm trong khoang t u

0,7 m/s den 1 m/s Goi A va B la hai diem nam tren Ox, a cung mgt phia so

v o i O va each nhau 10 cm Hai phan t u m o i truong tai A va B luon dao

dong nguge pha v a i nhau Toe do truyen song la

A lOOcm/s B 80cm/s C 85 em/s D 90em/s

C a u 9: Cho mot song ngang c6 phuong trinh song la u = 5cos

0,1 2

m m , trong do x tinh bang cm, t tinh bang giay Phan tic song M c6 X M = 3cm

a thai diem t = 2s c6 do dai

Van toe truyen song trong moi truong do c6 gia t r i

A 2m/s B Im/s C 0,5m/s D 3m/s

C a u 11: (De thi tot nghi^p nam 2009) M p t song ngang t r u y i n theo c h i l u

duong trye Ox, c6 phuang trinh song la u = 6cos(AM - G,02;w); trong do

u va X tinh bang cm, t tinh bang s Song nay c6 buac song la

A 150 cm B 50 cm C 100 cm D 200 cm

C a u 12: (De thi cao dkng nam 2009) M p t song truyen theo true Ox v o i

phuang trinh u = acos(47tt - 0,027tx) (u v ^ x tinh bSng cm, t tinh bang giay)

Toe dp truyen cua song nay la

A 100 cm/s B 150 cm/s C 200 cm/s D 50 cm/s

C a u 13: (De thi cao dkng nam 2008) Song ca c6 tan so 80 H z Ian truySn

trong mpt m o i truong v o i van toe 4 m/s Dao dpng cua cac phkn t u vat chat

tai hai diem tren mpt phuong truySn song each nguon song nhiJng doan Ian

lupt 31 c m va 33,5 cm, l?eh pha nhau goe

A — rad

2 B 71 rad C 2n rad D - rad 3

VAT lY 12 - T 6 M TAT I * THUYfT VA'BAI TAP TBAC H E H I E M - T A P I CHIfdNG 2: SdNE Clf

C a u 14: Tren soi day O A , dau A c6 dinh va dau O dao dpng dieu hoa c6

phuong trinh uo = 5cos(5 TC t) (cm) V a n toe truyen song tren day la 24cm/s

va gia su trong qua trinh truySn song bien dp song khong d6i Phuang trinh song tai d i l m M each O mpt doan 2,4cm la:

C a u 15 Tao song ngang tren mpt day dan hoi Ox M p t diem M each

ngu6n phat song O mpt khoang 50 cm c6 phuang trinh dao dpng

U M = 2eos[7r(t - 1 / 2 0 ) ] (cm), van toe truyen song tren day la 10 m/s Phuong

trinh dao dpng cua nguon O la:

A.uo = 2sin7c(t + 1/20) (em) B UQ = 2cos(7rt - 7r/20) (em) C.Uo = 2sin(nt - 7c/20 ) (cm) D UQ = 2cos7rt (cm)

VAN D E 3: GIAO THOA SONG VOI 2 NGUON K E T HOP

CUNGPHA

r

Giao thoa la su t6ng hop cua hai (hay nhieu) song ket hop trong

khong gian, trong do eo nhung cho c6 dinh ma bien dp song dupe tang cuong hoac b i giam bat (hay tri?t tieu)

D i l u kien giao thoa (dieu ki?n hai ngu6n k i t hop): Hai song phai

xuSt phat tir hai nguon ciing tan so, cung phumtg dao dong, c6 dp

lech pha khong dSi theo thoi gian

Bien dp song tong hap:

Trang 9

» A T It IZ - TtM TAT li THBYfT VA BAI TAP TRAC NGHIEM - TAP 1

V | tri cac diem dao dpng v6i bien d9 circ dai: (ggn Idi)

d^-d,=kX + Hi$u duang di bang so nguyen Idn buac song,

•y Vf tri cue dgi bac n itng vai k = n (v&i n = 0; ± 1; ± 2 )

• V | tri c^c diem dao d^ng vol bien d? eye tieu: (ggfn 16m)

d,-d,= .4

, 2) + Hieu duang di bdng s6 ban nguyen Idn buac song (so le ciia

nua buac song)

+ Vi tri cue tieu thii n ung vaik = n- 1 (vai n = I; 2; 3 )

Hinh anh giao thoa:

- 6 vi tri duang trung true eua Si va S2 luon la day e\re dai

- Ve 2 phia cua duang trung true la nhirng day euc dai va cue

tieu xen ke nhau hinh dang Hyperbol

- S6 cue dai tren doan S1S2: SiS^ <kX< S^S

- S6cvrctieutrendoanSiS2:

>A:= ?

SS gid tri cua k Id so cue dgi hay euc tiiu tren doan S1S2

- Khoang each giua hai c\rc dai lien tiep bang khoang each

gifta hai evrc tieu lien tiep tren doan S1S2 va bang —

Chii v; Neu hai nguSn dao dgng ngu(rc pha, ta doi cho cong thuc

eua cue dgi cho cue tieu va ngu^rc Igu

VAT Vi 1Z - TllH TAT tV THUYgT VA BAI TAP TBAC NBHIgM - TAP 1 CHirifRG I: SlNG Ctf

B a i tap m a u ; 6 mat nuac, c6 hai ngu6n k6t hop A, B dao dong theo

phuomg thang dung vai phuomg trinh u^=Ug^20co^{\Qnt){mm)

AB = 26em va t6e do truyen song la 50 cm/s Coi bien do song khong doi

khi song truySn di

a. Cac diem tren du6ng trung true cua AB dao dohg vai bien do bang bao nhieu?

b. Tinh bien do song t^i M 6 mSt nuac each hai nguon Ian luot la

21 cm va 26 cm

c. Tinh so e\rc dai va cue tieu nSm tren doan AB

d. Diem C va D nam tren mSt nuac sao cho ABCD la hinh vuong,

tinh s6 cue dai tren doan CD va AC

c6 6 gia tri cua k —* 6 circ tieu

d ABCD Id hinh vuong =>

CA = 26V2 vd CB = 26cm Xet CA-CB 26V2-26 A 10 = 1,076

=» diSm C nam giua cue dai bae 1 va bac 2 Do do, s6 c\rc dai gifta C va duang trung trye eua AB la 1, nen:

- S6 cue dai tren doan CD: 3

- So cue dai tren doan CA: 4

Trang 10

CHI/ITNG Z: SdNG cd VAT LY I Z - T O M T A T lY THDYgTVA BAl TAP TRAC NCHlgM-TAPI

B a i tap 3 :

Cau 1: (De thi cao d5ng nSm 2009) CJ mat nu6c c6 hai ngu6n song

dao dong theo phuomg vuong goc voi mat nuac, c6 cung phuomg trinh

u = Acoscot Trong mien gap nhau cua hai song, nhung diem ma a do cac

phan tu nuac dao dong voi bien dp cue dai se c6 hi?u duang di cua song tu

hai nguon den do bang

A mot s6 le \hn nua buac song

B mgt s6 nguyen Ian buac song

C mgt so nguyen Ian nua buac song ;

D mot so le Ian buac song

Cau 2: (De thi dai h^c nam 2007) DS khao sat giao thoa song ca, nguai ta

b6 tri tren mat nuac nam ngang hai ngu6n ket hgp Si va Si Hai ngu6n na)'

dao dong dieu hoa theo phuang thang dung, ciing pha Xem bien do song

khong thay doi trdng qua trinh truySn song Cac diem thuoc mat nuac va

nam tren duang trung true cua doan S1S2 se

A dao dpng vai bien dp bang nua bien dp cue dai

B dao dpng vai bien dp cue tieu

C dao dpng vai bien dp cue dai

D khong dao dpng

Cau 3: T^i hai diem A va B tren mat nuac c6 2 ngu6n song giong nhau v o i

bien dp a, buac song la 10cm Diem M vai M A = 25cm va M B = 5cm s£

dao dpng vai bien dp

A 2a B a C.-2a D 0

Cau 4: Trong thi nghifm giao thoa song bai 2 nguon ket hap A, B tren mat

thoan^ ciia 1 chk long dao dpng theo phuang trinh u = acos(1007rt) (cm),

van toe truyen song v = 0,6m/s Xet 1 dilm M c6 hi?u duang di M A - MB =

3cm Tinh tir duang trung tryrc cua AB, dilm M nam tren

A Cue tieu bac 3 B Cue dai bac 2

C C\rc t i l u bac 2 D Cue dai bac 3

Cau 5 : 6 mat nuac, c6 hai nguon ket hpp A, B dao dpng theo phuang than;.'

dumg voi phuang trinh = Ug = 20cos(l07rt)[mm) Toe dp truyen song la

80 cm/s Coi bien dp song khong doi khi song truyen di Phan tu M a

ma'-nuac each hai ngu6n Ian lupt la 21 cm va 29 cm c6 bien dp dao dpng la

A 0 mm B 40 mm C 30 mm D 20 mm

7A

yAT I t 1Z - TiM TAT lY THUYfT VA BAI TAP THAC II8H|£M - TAP 1 CHlTKNG Z: SdNG Cd

I

Cau 6: Trong thi nghi?m tao van giao thoa song tren mat nuac, nguai ta

dung ngu6n dao dpng c6 tan so 100 Hz va do dupe khoang each giua hai ggn song lien tiep nam tren duang n6i hai tam dao dpng la 4 mm Van t6c song tren mat nuac la

A 0,2m/s B 0,4m/s C 0,6 m/s D 0^8 m/s

Cau 7 : Mot nguai lam thi nghiem voi mot chat long va mot chn rung eo t&i

so 20Hz Giua hai diem Si, S2 nguai do dim dupe 12 hypebol quy tich cua cac diem dung yen Khoang each gitta dinh cua hai hypebol ngoai cung la 22cm Toe dp truyen song la

A 70em/s B 80cm/s C 7cm/s D 8cm/s

Cau 8: (De thi cao dang nSm 2008) Tai hai d i i m M va N trong mot moi

truang truyen song c6 hai ngu6n song ket hpp cung phuang va cung pha

dao dpng Bih bien dp, van toe cua song khong doi trong qua trinh truygn,

tan so cua song bang 40 Hz va c6 s\ giao thoa song trong doan M N Trong

dpan M N , hai diem dao dpng c6 bien dp cue dai gan nhau nhk each nhau

1,5 em Van toe truySn song trong moi truang nay bang

Cau 10: Trong thi nghiem giao thoa song tren mat nu6c, hai ngu6n kk hgp

A, B dao dpng vai t i n so 20 Hz, cung pha, tai mpt diem M each A va B Ian luot la 16cm va 20cm, song c6 bien dp c\rc dai, giiJa M va duang trung true cua AB CO 3 day cue dai khac Van toe truyen song tren mat nuac la

I A 20 cm/s B 26,7 cm/s C 40 cm/s D 53,4 em/s

Cau 11: Tren mat nuac n l m ngang, tai hai diem S,, Sj each nhau 8,2 cm,

nguai ta dat hai ngu6n song ca ket hpp, dao dpng dieu hoa theo phuang

thang dung c6 t i n s6 15 Hz va luon dao dpng d6ng pha BiSt wan toe

truygn song tren mat nuac la 30 cm/s, coi bien dp song khong d6i khi

truyen di S6 dilm dao dpng vai bien dp cue dai tren doan SjSj la

A 11 B 8 C 5 D 9

75

Trang 11

CHtfirH6Z:Stl8Cf WAT it M - TJM TAT It THBYgT t* BAI T A P TBAC NGRlfM - T A P 1

Cau 12: (De thi cao dfing niin 2010) (5 mat thoang cua mpt chat 16ng c6

hai nguon kk hgp A va B dao dpng deu h5a cung pha voi nhau va theo phuomg

thSng dung Bik toe dp truyen song khong doi trong qua trinh Ian tmyen, bu6c

song do moi ngu6n tren phat ra bling 12 cm Khoang each ngSn nhlt giiJa hai

dilm dao dpng voi bien dO cvre dai nSm tren doan thSng AB la

A 9 em B 12em C.6cm D 3 cm

Cau 13: (De thi d^i hffc nSm 2009) hai diem A va B each nhau lOem

tren mSt chat long c6 hai ngu6n phat dao dpng theo phuong thing diing v6i

cac phuomg trinh la UA = 0,5sin(507rt) cm ; UB = 0,5sin(507rt + n) cm, v§n t6c

truyen song tren mSt chit long Ik 0,5m/s Xac dinh s6 diem c6 bien dp dao

dOng cure dai tren doan thSng AB

A 12 B 11 C 10 D.9

Cau 14: Trong mpt thi nghi?m giao thoa song tren m5t nuac, c6 hai ngu6n

k6t hgrp A va B dao dpng cung pha voi tin s6 f = 20Hz, cdch nhau 8cm Van

t6c truyen song tren mat nuac v = 30cm/s Gpi C va D la hai diem tren mat

nuae sao cho ABCD la hinh vuong S6 diem dao dpng voi bien dp eye dai

tren doan CD la:

A 11 diem B 5 diem C 9 diem D 3 diem

Cau 15: (De thi dai hQc nSm 2010) 6 mat thoang cua mpt chat long c6 hai

nguon song ket hgp A va B each nhau 20cm, dao dpng theo phuomg thing

dung voi phuong trinh U A = 2cos(407rt) va UB = 2cos(407it + 7t) ( U A vd UB

tinh bing mm, t tinh bing s) Biet t6c dp truyen song tren mat chat long la

30 cm/s Xet hinh vuong AMNB thupc mat thoang chat long- So dilm dao

dpng voi bien dp c\rc dai tren doan BM la

A 19 B 18 C.20 D 17

^ VANDE4:S6NGDirNG

• W^t can CO dinh: Song toi va song phan xa ngupc pha (ngupc

diu)

• Song dung c6 dupe la do s\ giao thoa cua song tdi va song

phan xa cung phat ra tu mpt nguon, tao cac nut va cac bung

• Khoang each gifta hai niit liSn tiep = khoang each giira hai

b\mg lien tiep = —

VAT It K - Till TAT li TIWTfT VA BAI TjP T«Ac BGHItM - TJP1 CHIMMG Z: StNG Cll

Khoang each giila nut va bving lien tiSp = —

Khoang th6i gian giOra hai Ian lien tiep spi day duoi thing la T/2

Song dung tren sgi day v6i hai d4u 1^ 2 nut (2 dau c6 djnh):

l = n— 2 n=s6bung= (So nut)-1

S6ng dimg tren spi day v6i mpt dau la nut, mpt diu la bvmg (mpt dau dao dpng t\ do):

n=s6 niit = so b^ng

, X X

l = n

2 4

Bai tap mau; Spi day dan hoi AB = 2m c6 dau B c6 djnh, diu A dao

dpng voi tan so lOOHz Tren day c6 song dimg, diu A xem nhu mpt nut song Ngudi ta thay ngoai 2 diu day eo dinh con c6 3 diem khac luon dumg yen

a Tinh van toe truyin s6ng

b Mpt diem M cdeh diu A mpt doan 0,75m, hoi M la nut song hay b\mgs6ng

c Thay doi tin so dao dpng or A den gia trj 50Hz tren day van c6 song dimg, hoi tren AB c6 bao nhieu nut song

Giai:AB = 2m

5 nut ^ 4 bung n = 4:1 = 4^ => X = Im v = Xf = 1.100 =

a lOOm/s

b = 2£5 = 1^5 M \k byng s6ng thii 2 ke tu A

X/2 1/2

c X = ^ = ^ = 2 m ; l = n^=>n = f = 2-»2bvng-.3nut Bai tap 4:

CSu 1: S(?i day dan hoi AB c6 diu B c6 djnh Dau A dupe rung vdi tin s6 f

tgo mpt song tdi t^ B c6 phuomg trinh Ui = acos(2nft) S6ng phan x? t^i

B c6 phuong trinh

Trang 12

cmm Z:Sfll«BCtt yAT LY 12 - TOM TAT LY THUVeT VA BAI TAP TRAC N6HieM - TAP 1

A U2 = acos{2nft + n) B U2 = acos(2nft)

C U2 = —asin(2nft) D U2 = asin(2nft)

Cau 2: Sgi day dan hoi A B c6 chieu dai / voi dau B c6 dinh Dau A dugc

rung vai tan so f tao mot song toi tai B co phuong trinh = acos(2nft)

Song phan xa tai A co phuong trinh

A U2 = acos (inft + B U2 = acos (inft +

C U2 = -acos {inft - D U2 = asin (Znft —

Cau 3: Dieu kien xay ra song dung tren sgi day dan hoi hai dau co dinh la

A Buac song gap doi chieu dai day

B Buac song bang so ban nguyen Ian chieu dai day

C Chieu dai day bang so nguyen Ian VA buac song

D Chieu dai day bang so nguyen Ian nua buac song

Cau 4: (De thi tot nghi^p nam 2007) Khi c6 song dung tren mpt sgi day

dan hoi thi khoang each giua hai bung song lien tiep bSng

A mpt phan tu buac song B mpt buac song

C nua buac song D hai buac song

Cau 5: Quan sat song dimg tren mot sod day dan hoi, nguoi ta thay khoang

thai gian giiia 2 thai diem gan nhat ma day duoi thang la 0,2 s, khoang each

giira 2 cho luon dung yen ke nhau la 10 cm Toe do truyen song tren day la:

A.25cm/s B.lOOcm/s C.20 cm/s D.50 cm/s

Cau 6: Tren mgt S(?i day co chieu dai / , hai dau co djnh, dang co song

dung Tren day c6 mgt bung song Biet t6c truyen song tren day la v

khong doi Tan so cua song la

A — B. —. C —. D -

Cau 7: thi cao d5ng nam 2010) Mpt sqti day chiSu dai i cSng ngang,

hai dau co djnh Tren day dang c6 song dung voi n b\mg song, toe dp truyen

song tren day 1^ v K h o ^ g thai gian giiJa hai Ian lien tiep sgi day duoi thing la

n£ £ 2nv nv

71

J LY 12 - TdM TAT lY THUYfT VA BAI TAP TRAC NEHlgM-TAP 1 CHIfdNB 2: SONG Cd

Cau 8: (De thi cao dang nam 2010) Mpt sai day A B c6 chieu dai 1 m

cang ngang, dau A co dinh, dau B g i n voi mgt nhanh cua am thoa dao dgng

digu hoa vai tan s6 20 Hz Tren day A B co mot song dung 6n djnh vai 4

bung song, B dugc coi la nut song Toe dp truyen song tren day la

A 50 m/s B 2 cm/s C 10 m/s D 2,5 cm/s

Cau 9: Mgt sgi day dan hoi dai 60 cm rung vai tan so 50 Hz tren day tao

thanh song dung 6n dinh vai 4 bung song, hai dau la 2 nut song Van t6c song tren day la '

A 12 cm/s B "60 cm/s C 75 cm/s D 15 m/s

Cau 10: Tren mgt sgi day dan hoi dai 1,8m, hai dau co dinh, dang co song

dimg vai 6 bung song Biet song truyen tren day c6 tan so 1 OOHz Toe dp truySn song tren day la :

A.20m/s B 600m/s C 60ni/s D lOm/s

Cau 11: (De thi dai hpc n5m 2008) Trong thi nghiem ve song dimg, tren

mpt sgi day dan hoi dai 1,2m vai hai dau co dinh, ngudi ta quan sat thay ngoai hai dau day co dinh con co hai diem khac tren day khong dao dpng Biet khoang thai gian giiia hai Ian lien tiep vai sgi day duoi thang

la 0,05 s Van toe truyen song tren day la

A 8 m/s B 4m/s C 12 m/s D 16 m/s

Cau 12: Mgt sgi day AB dai 100 cm cang ngang, dau B co djnh, dau A gin

voi mgt nhanh cua am thoa dao dgng dieu hoa vai tan so 40 Hz Tren day

AB CO mgt song dung on djnh, A dugc coi la nut song Toe dg truyen song

tren day la 20 m/s ca A va B, tren day c6

A 3 nut va 2 bung B 7 nut va 6 byng

C 9 niit v^ 8 byng D 5 mit va 4 byng

CSu 13: Mgt day A B hai d i u c6 dinh AB = 50cm, v$n t6c truyen song tren

day Im/s, tan so rung tren day lOOHz Diem M each A mpt doan 3,5cm la hay b\mg song thu may ke tir A :

A Nut song thu 8 B Bung song thur 8

C Nut s6ng thii 7 D B\mg song thu 7

Cfiu 14: MOt sgi day A B = / m treo l a lung bai mgt d i u A co g i n mgt can

v6i tan so f = 40Hz, dau B dao dgng t\ do Quan sdt s6ng dimg tren

% c6 5 b6 s6ng, v$n toe truyen song tren day 1^ lOm/s Khi d6 chiSu dai

% va s6 nut s6ng trSn dSy 1^:

78

Trang 13

CHinMGKStlKCtf Ul I t 1Z - TOM TAT U THBYfT V * BAI TAP TRAC MeHlgM - TAP t

A / = 62,5cm, 6 nut s6ng B / = 62,5cm, 5 niit s6ng

C / = 68,75cm, 6 nut song D / = 68,75cm, 5 nut song

Cau 15: (De thi dai hgc nam 2011) Mot sgi day dan hoi cang ngang, hai

dau CO dinh Tren day c6 song dung, t6c dp truyen song khong doi Khi tan

s6 song tren day la 42 Hz thi tren day c6 4 diem b\mg Neu tren day c6 6

diem b\mg thi tkn so song tren day la

A 252 Hz B 126 Hz C 28 Hz D 63 Hz

A V A N B E 5 ; S 6 N G A M

• Song am la nhGng son^ ca truySn trong moi trucmg khi, long,

ran Song am c6 cung tan so voi ngu6n am

• Am nghe dugc c6 tan so tir 16Hz den 20.000Hz va gay ra cam

giac am trong tai con nguoi

• Ha am: Nhihig song ca hpc t3n s6 nho horn 16Hz ggi 1^ s6ng ha

am, tai nguoi khong nghe dugc

• Sieu am: Nhftng s6ng ca hgc tan so l&n hem 20.000Hz goi \h

song sieu am, tai nguoi khong nghe dugc

• Nhac am c6 tan so xdc dinh Tap am khong c6 tan so xdc dinh

• Song am truyen tot nhat trong chat rSn, roi den chit 16ng va sau

cung la chat khi Song am khong truyen dugc trong chan khong

• T i n so s6ng am khong thay d6i khi truyen qua cdc moi

trudng khdc nhau

Cvtimg dO am (I) t ^ mgt diem 1^ d^i lugng do bSng lugn^ nSng

lugng ma song am tai qua mgt don vj dien tich d5t t^i diem do,

vuong goc v6i phuong truyen s6ng trong mgt don vj thdri gian

Don v} cuong dg am la W/m^ Cuong dg am ti 1? nghjch voi

binh phuong kho^g each den nguon

2

Trong do dj va d2 Idn lu0 la khoang each tic diim dang tinh

cudng dg dm din nguon

Mii-c cu"6tig dO am (L): Miic cuong dg am L la dai lugng de so

sanh dg to cua am nghe dugc c6 cuong do I voi dg to cua am chuan c6 cuong do IQ

1(^5) = 10 Ig— IB = lOdB

D Q cao cua am: Ph\ thugc vao tan so cua am Am cao (hoac

thanh) c6 tSn so Ion, am thap (hoSc trSm) c6 tan so nho

Do to ciua am: Gin lien voi die trung vat ly miic cuong dg am

Am sac: Giup ta phan bi?t am do cac nguon khac nhau phat ra

Am sic CO lien quan mat thidt voi do thi dao dong am

Bai tap 5 : Cau 1: (De thi tot nghifp nam 2008) Mot song am truyen tir khong khi

vao nuoc thi

A tan so va buoc s6ng deu thay doi

B tan so thay doi, con buoc song khong thay doi

C tan so khong thay doi, con buoc song thay d6i

D tan so va buoc song deu khong thay d6i

Cau 2: Lugng nang lugng dugc song am truyen trong mgt don vj thoi gian

qua mgt don vi di?n tich dat vuong goc voi phuong truySn am ggi la:

A Cuong dg am B Dg to cua am

C Muc cuong dg am D NSng lugng am

Cau 3: Mgt la thep mong, mgt dau c6 dinh, dau con lai dugc kich thich d8

dao dgng voi chu ky khong d6i va bang 0,08 s Am do Id thep phat ra la

A am ma tai nguoi nghe dugc B sieu am

C h? am D nhac am

Cau 4: Di§u nao sau day sai khi noi vh dac trung cua cua am ?

A Dg cao cua am phy thugc vdo tin s6 cua am

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CHIfdNG 2: SONG Cd VAT LY 12 - TdM TAT LY THUYfT VA BAI TAP TRAC WfiHlfM - TAP 1

C Am sac ph\ thuQC vao d ^ g do thi cua am

D Nang lugng ciia song am khong thay doi khi song am truySn di

Cau 5: Chon cau tra iai sai •

A Song am la nhiSng song ca hoc dpc Ian truyen trong moi tnrong

vat chat, CO tan s6 tir 16Hz d6n 20.000Hz va gay ra cam giac am

trong tai con nguai

B Song am, song sieu am, song ha am c6 cung ban chat vat ly

C Song am truyen dugc trong mpi moi truong vat chat dan hoi ke

ca chan khong

D Toe do truyen am trong chat r3n thuong Ion hon trong chat long

va trong chat khi

Cau 6: Khi noi ve song am, phdt bilu n^o sau day la sai?

A Toe do truyin song am trong khong khi nho hom t6c dp truyen

song am trong nuac

B Song am truyen dugc trong cac moi tnrong rSn, long va khi

C Song am trong khong khi la song dpc

D Song am trong khong khi la song ngang

Cau 7: (De thi tot nghi?p nam 2010) Khi n6i \h sieu am, phat bieu nao

sau day sai?

A Sieu am c6 the truyen dugc trong chit rin

B Sieu am c6 tan so Ion hem 20 kHz

C Sieu am c6 the truyen dugc trong chan khong

D Sieu am c6 the bi phan xa khi gap vat can

Cau 8: Vai lo la cuong dp am chuan, 11^ cuong dp am Khi muc cuong dp

am L = 2 Ben thi:

A.I = 2Io B.I=-Io C.I=10^Io D.I=10-2lo

2

Cau 9: Tai dilm A c6 muc cudng dp am la 90 dB, biet nguong nghe cua

am do la 16"'^ W/m^ Cuemg dp am t^ii A la:

A./^ =0,01 W/ml B = 0,001 W/ml

C = 10-' W/ml D- = 10" W/ml

82

VAUy - TAT LY THUYfT VA BAI TAP TBAC llBHigM - TAP 1 CHIfdNG 2: SDNG Cd

CSu 10: Khi muc cuong dp am tang 20dB thi cu6fng dp am tang:

A 2 Ian B 200 lin C 20 lin D 100 Ian

CSu 11: Khi cuong dp am tang gap 1000 Ian thi muc cuong dp am tang :

A lOOdB B.20dB C.30dB D 50 dB

CSu 12: Nguoi ta do dugc muc cuong dp am tai diem A la 90 dB va tai

dilm B la 70 dB Ti 1? cuemg dp am tai A va B la

Cau 13: (De thi dai hgc nSm 2009) Mpt s6ng am truyen trong khong khi

Mure cuong dp am tai diem M va tai diem N lin lugt 1^ 40 dB va 80 dB Cucmg dp am tai N Ion hon cuong dp am tai M

A 10000 Ik B 1000 Ian C 40 Ian D 2 Ian

Cau 14: (De thi d^i hpc nSm 2010) Ba diem O, A, B ciong nam tren mpt

nvra duong thang xuit phat tir O Tai O dat mpt ngu6n diem phat song am ding huong ra khong gian, moi truong khong hap th\ am Mure cuong dp

am tai A la 60 dB, tai B la 20 dB Muc cuong dp am t^i trung diem M cua

doan AB la

A.26dB B 17dB C.34dB D.40dB

Cau 15: Muc cuong dp am do nguon S gay ra tai diem M la L, khi cho S

tiSn lai gin M mpt doan 62m thi miic cudng dp am tang them 7dB Khoang cdch la S den M c6 gia tri xap xT la:

A 210m B.209m C 112m D 42,9m

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