Tài liệu Hướng dẫn giải chi tiết đề thi tuyển sinh đhcđ môn vật lý-phan văn huấn

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530.076 PHAN VAN HUAN H561D HlidNG DAN GIAI CHI TIET DE THI TUYEN SINK DAI HOC. CAO B&NC VAT LI H Nha xuat ban Dai hoc Quoc gia Ha NOi bJO. 01±__ '-W5t>/< 0 PHANVANHUAN DE THI DAI HQC - CAO DANG M6n VAT LI NHA XUAT BAN DAI HQC QUOC GIA HA NQI N H A X U A T B A N DAI H Q C Q U O C G I A H A NOI 16 HANG CHUOl - HAI BA T R U N G - HA NOI Dien thoai: Bien tap - Che b a n : (04) 39714896 Hanh chi'nh: (04) 39714899. Tonq bien t a p : (04) 39714897 Fax: (04) 39714899 Chiu trach nhi$m xuat ban: Giam doc - Tdng bien tap: tap: PHAM TH! TRAM Nha sach S A O MAI Doi tac lien l Vi. Neu chieu dong t h d i h a i bufc xa t r e n v^o qua cau t h i d i $ n the cifc dai cua no chi hang d i e n the I d n hcfn, do c h i n h la V2. Vdy chon dap an A. Cdu 2: T r o n g t h i n g h i e m ve song dCrn^, t r e n m o t stfi day d a n h 6 i d^i 1,2 m v d i h a i dau co d i n h , ngUdi t a quan sat t h a y ngoai h a i dau day co d i n h con co h a i d i e m khac t r e n day k h o n g dao dong. B i e t k h o a n g t h d i gian giOfa h a i I a n l i e n tiep sgti day duoi t h i n g l a 0,05 s. V a n toe t r u y e n song t r e n day l a : A. 16 m/s. B. 4 m/s. C. 12 m/s. D . g m/s. Giai Theo de b a i t h i t r e n day tao t h a n h 3 m u i song, m o i m i i i s6ng co chieu dai —. 2 T a c o : 3 - = 1,2 = > = 0,8m. 2 Khoang t h d i gian giffa h a i I a n l i e n t i e p stfi day a j 6 j t h i n g l a 0,05s nen t a co chu k i T = 0,05.2 = 0,1s. V a n toe t r u y e n song t r e n day: ^ 5i, = ^ 0 8 ~ "QT ~ ^C™'^)' Vdy chon dap an D. Cdu 3: Doi v d i SLT Ian t r u y e n song dien tCf t h i A. vector ciTdng do dien triJdng E va vectcf cam ufng tCr B luon vuong goc v d i phtTcfng t r u y e n song. Giai Chi tiSt (3e thi TS DH, CO M6n vat li 3 B. vectcf CLfcrng do d i e n triTcfng E va vecto cam ufng tiT B luon cung phiiong vdfi phiTctog t r u y e n song. C. vector cam ufng tif B cung phLfcrng vdri phirorng t r u y e n song con vector CLTcfng do dien t r i / d n g E vuong goc v d i vector cam ufng ttf B . D. vectcf cifcfng do dien tn/cfng E cung phtfcfng v6i phiromg truyen song c6n vector cam ufng tCf B vuong goc vdri vector ci/orng do dien trUdng E . Giai D o i v d i suf Ian t r u y e n song dien tCf t h i vecto cifdng do dien triicfng E va vector cam ufng tCr B luon vuong goc vdri phiTorng t r u y e n song. Vay chgn dap an A. Cdu 4: Cof n a n g cua m o t v a t dao dong dieu hoa: A. t a n g gap doi k h i bi§n do dao dong cua v a t t a n g gap doi. B. b i e n t h i e n t u a n hoan theo t h d i gian v 6 i chu k y b k n g chu k y dao dong cua v a t . C. b i e n t h i e n t u a n hoan theo thofi gian v d i chu k y bSng mot nufa chu k y dao dong cua vat. D . b a n g dong nSng cua v a t k h i v a t id'i v i t r i can bang. GiSi Cor n a n g cua m o t vat dao dong dieu hoa bang dong nang cua vat k h i v a t tdri v i t r i can bang. Vay chgn dap an D. Cdu 5: H a t n h a n '°Be c6 k h o i liTcrng 10,0135u. K h o i lifgng cua ncftron ( n a t r o n ) m n = l , 0 0 8 7 u , k h o i Itrcrng cua p r o t o n ( p r o t o n ) mp = l , 0 0 7 3 u , l u = 931 MeV/c^. N a n g liTcfng l i e n k e t r i e n g cua h a t n h a n '"Be D . 632,1531 MeV. C. 6,3215 M e V . B. 63,2152 MeV. A . 0,6321 M e V . la: Giai N a n g Itfdng l i e n k e t r i e n g cua h a t n h a n '°Be l a : «' AC (6m„+4m -meJ.QBl AJb^V ^ = 6,3215MeV. A Vay chgn dap A an C. Cdu 6: P h a t bieu nao sau day la s a i k h i n o i ve nang liidng dao dong dien tii t i i (Jo (dao dong rieng) t r o n g mach dao dong dien tCr LC k h o n g CO dien trcf thuan? 4 Giai Chi tiet de thi TS DH, CD M6n Vat li A. tl^.ng luang tCr trifcfng cure dai b k n g n a n g Itfong d i e n tCr cua mach dao dong. B. N a n g Itfcfng dien trtf&ng va n a n g Itftfng tCr t n f o n g b i e n t h i e n dieu hoa vdfi t a n so bSng mot nijfa t a n so cua ctfcfng do dong dien t r o n g mach. C. K h i nSng lifcfng dien trtfcrng g i a m t h i n a n g liitfng tCr trifcrng t a n g . D. Nang Itfofng dien tii cua mach dao dong bkng tong nang liigfng dien tnfcfng tap trung cf t u dien va nang li/cfng tCr tnicfng tap trung cf cugn cam. Giai V i n a n g lifcfng dien triicfng va nSng Itfofng tCf triXdfng b i e n t h i e n dieu hoa v6i chu k i bang mot nufa chu k i cifcfng do dong dien t r o n g mach nen tan so cua no p h a i gap doi t a n so cua cifdfng do dong dien t r o n g mach. Vdy chqn dap an B. Cdu 7: T i a Rcfnghen c6 A. cung b a n chat v 6 i song v6 tuyen. B. cung ban chat vdfi song a m . C. dien t i c h a m . D. btfdfc song Idfn hcfn biTdfc song cua t i a h o n g ngoai. Giai T i a Rcfnghen la bufc xa dien tii n e n k h o n g m a n g d i e n , c6 cung b a n chat vdfi song v6 tuyen va c6 bildfc song nho hofn biidfc song cua t i a hong ngoai. Vdy chon dap an A. Cdu 8: H a t n h a n A dang dufng yen t h i p h a n r a t h a n h h a t n h a n B c6 k h o i lifong ms va h a t a c6 k h o i lucfng m„. T i so giOfa dong n a n g cua h a t n h a n B va dong n a n g cua h a t a ngay sau p h a n r a b k n g : . A. ^ . c. B. m„ D. ^ Giai Ap dung d i n h l u a t bao toan dong liJcfng cho h a t dang dufng y e n , t a c6: mBVB = m„v„. T i so giufa dong n&ng cua h a t n h a n B va dong nSng cua h a t a ngay sau p h a n r a l a : ^ Vdy chqn dap an D. Giai Chi tiet de thi T S B H , C D M6n Vat II = - Cdu 9: Cho doan mach di$n xoay chieu gom cuon day c6 dien trd thuan R , m^c nol tiep v6i tu*dien. Biet hieu dien the giffa hai dau cuon day lech pha — so v6i hi|u dien the giuTa hai dau doan mach. Moi lien h$ giiJa dien tror thuan R vdri cam khang Z L cua cuon day dung khdng Zc cua tu dien la: ' D . R=^ = ZC(ZL - C. R ' = Zc(Zc - ZL). ' E. R2 = ZL(ZC - Z L ) . A. R ' = ZL(ZL - Zc). Zc). 2 Do lech pha giffa hai dau cuon day: tancp, = —^. R Z Do l$ch pha giffa hai dau doan mach: tan(p = — -Z -. R Theo gia thiet 9, +(p = — nen ta c6: cot(p, =tan(p =>^=^^-^R^=z,(z,-zJ. Vdy chqn dap an B. Cdu 10: Hat nhan ^^X ph6ng xa bien thanh mot hat nhan ^^^Y ben. Coi khoi lifcfng cua hat nhan X , Y bang so khoi cua chung tinh theo dcfn v i u. Biet chat phong xa X c6 chu k i bdn ra 1^ T . Ban dau c6 mot khoi lifcfng chat ^^X, sau 2 chu Id ban ra t h i t i so giffa khoi Iffdng cua chat Y A. 4 - ^ . Aj khoi lUcfng cua chat X la: B. 3 ^ . A, C. 4 ^ . A, Sau 2 chu kX, so hat nh^n X c6n lai 1^: D. = T i so' kho'i Ifftfng cha't Y • • X la: = 3^. Aj = So hat nhan cua chat Y hinh th^nh la: N„ = N * Vdy chon dap an B. N^A, ^ = -N^. = 3^. A, ^ 6 G i 4 i c h i l i S t ( J « t h i T S B H , C D M 6 n V$t« Cdu 11: M o t v a t dao dong dieu hoa c6 chu k i l a T . N e u chon goc thcfi gian t = 0 l a luc v a t qua v i t r i can bang, t h i t r o n g nufa chu k i dau t i e n , van toe cua v a t b k n g k h o n g of t h d i diem: T A. t = - . 8 B.t=I. C.t= 4 T -. 6 D. I. 2 Giai 1 Chon goc t h d i gian t = 0 l a luc v a t qua v i t r i can b k n g , t h i — chu k i nufa v a t se tcri b i e n v a v a n toe b k n g k h o n g . T r o n g nufa chu k i dau T tien, v a n toe cua v a t b k n g k h o n g d thdi diem t = —. 4 Vdy chon dap an B. Cdu 12: M o t l a t h e p mong, m o t dau co d i n h , dau con l a i diJtfc k i c h t h i c h de dao dong v d i chu I d k h o n g doi va b k n g 0,08 s. A m do l a t h 6 p phat r a l a : A. sieu a m . B. ha am. C. nhac a m . D. a m m a t a i ngifdi nghe diftfc. Giai T a n so a n . do t h e p p h a t r a : f = - = — ^ = 12,5 < 16Hz. T 0,08 T a i ngifori k h o n g t h e nghe di/grc a m co t a n so dtfdi 16Hz n e n a m do la thep p h a t r a l a h a a m . Vdy chon dap an B. Cdu 13: P h a t bieu nao sau day l a s a i k h i n 6 i ve do p h o n g x a (hoat d6 phong xa)? A. Dcfn v i do do phong xa l a beccfren. B. Do phong xa l a d a i luang dac trifng eho t i n h p h o n g xa m a n h hay yeu cua m o t li/cfng chat phong xa. C. Vdri m o i iLfotng chat phong x a xAc d i n h t h i dp p h o n g x a t i le vdri so nguyen tuf cua liTcfng chat do. D. E)o phong xa cua m o t lacfng chat ph6ng xa p h y thuoc n h i $ t dp cua lUtfng chat do. Giai Do phong x a cua m o t li/tfng chat phong x a k h o n g p h u thuoc v k o cdc tac dong b e n ngoai nhtf n h i e t do, ap suat, a n h sang,... Vdy chon dap an D. GIJichitiStdlthiTSDH, CDMdn V l L t l f 7 Cdu 14: Doan mach dien xoay chieu khong phan nhanh gom a/^n day C O do tir cam L , dien t r d thuan R va tu dien c6 dien dung C. K h i dong dien c6 tan so' goc chay qua doan mach t h i he so cong suat cua doan mach nay A. bang 0. B. phu thuoc dien trof thuan cua doan mach. C. b k n g l . D. phu thuoc tong irb cua doan mach. GiSi K h i dong dien c6 tan so goc chay qua doan mach t h i xay ra hi^n tiTtfng cong hLfomg. K h i do u, i cung pha va he so cong suat cua doan mach bang 1. Vdy chgn dap an C. Cdu 15: Cho hai dao dong dieu hoa cung phiTcfng, cung tan so, cung bien do va c6 cac pha ban dau la — va - —. Pha ban dau cua dao dong 3 6 tong hcfp hai dao dong tren bkng: A. ^ . 12 B. ^ . 6 C. 2 D. ^ . 4 Giai Pha ban dau cua dao d6ng tong hap hai dao dong tren bang 7t 12 Vdy chgn dap an A. Cdu 16: Trong mot mach dao dong LC khon^ c6 dien t r d thuan, c6 dao dpng dien tii ttf do (dao dong rieng). Hieu dien the CLTC dai gifla hai ban tu va ctr&ng do dong dien ciJc dai qua mach Ian Itfcft la Uo va I Q . T Tai thdi diem ctfofng do dong dien trong mach c6 gia t r i y t h i do 16n hieu dien the giiJa hai ban tu dien la: A. ^ U o . C.iu, B. |Uo. 8 D . ^ U , . Gi^i Chi ti^t de thi T S B H , C D IVIon Vat If Giai cu nen W = Wd + Wt O Wt = W - Wa cu' 2 LI' LI' 8 2 8 2 Vay chgn dap an D. Cdu 17: Trong quang pho cua nguyen tuf hidro, neu biet h\idc song dai nhat cua vach quang pho trong day Laiman la X, i va h\i6c song cua vach ke vdfi no trong day nay la ^2 thi h\idc song pho cua vach quang trong day Banme l a : A. (X,-^,)- c. B. + D. Giai Difa vac scf do chuyen mufc nSng Iifpng, ta c6: hfi = E i - E o (1) hf2 = E2 - Ee (2) hf„ = E2 - E l (3) E3- E2- K Ei- TrCf ve vdi ve (2) va (1) ta difpc: Eo- hf„ = hf2 - hfi 1-v he ^ he he V i hf = — nen — = he . =>^„ = Vay chgn dap an B. Cdu 18: Phat bieu nao sau day l a s a i k h i noi ve dao dong cua con iSc dcfn (bo qua liic can cua moi triTdng)? A. Vdri dao dong nho thi dao dong cua con lac l a dao dong dieu h6a. B. K h i vat nang d vi tri bien, cd nang cua con lac bang the nang cua n6. C. Chuyen dong cua con iSc tCf vi tri bien ve vi tri can bang la nhanh dan. D. K h i vat nang di qua vi tri can bang, thi trong ILTC tac dung len no can Vlng vdi life cSng cua day. Giai Chi l e t d6 thi TS DH, CD Mdn V$t If 9 Khi vat nSng di qua v i t r i can bang, do chuyen dong tren cung tr6n nen hap life cua P v^ sufc cSng T tao thknh life hirdmg tam. V i v^y, trong liic t^c dung len no khong can bkng vdri lire cang cua day. Vay chon dap an D. Cdu 19: Trong nguyen tuf hidro, Mn kinh Bo la ro = 5,3.10""m. Ban kinh quy dao dCifng N la: D. i32,5.10-"m. C. 21,2.10-"m. B. 84,8.10-"m. A. 47,7.10-" m. Giai Ban kinh quy dao dCtog N la: r„ = n\ 16ro = 84,8.10-"m. Vay chon dap an B. Cdu 20: Mot chat phong xa c6 chu ky ban ra la 3,8 ngay. Sau thcfi gian 11,4 ngay t h i do phong xa (boat do phong xa) cua liTong chat phong xa con lai bSng bao nhieu phan trSm so v6i do phong xa cua lirang chat phong xa ban dau? A. 12,5%. ' B. 25%. C. 75%. D. 87,5%. V i 11,4 ngay tifdng uTng vdi 3 chu k i T nen dc phong xa con lai la: H = ^ = ^ = 12,5o/oH, Vay chon dap an A. ° Cdu 21: Neu trong mot doan mach dien xoay chieu khong phan nhdnh, ciicfng do dong dien t r i pha so vdri hieu dien the giUa hai dau doan mach, t h i doan mach nay gom A. tu dien va bien t r d . B. dien tror thuan v^ cupn cam. C. cuon day thuan cam va tu dien vdi cam k h ^ g nho hcfn dung khang. D. dien t r d thuan va tu dien. Neu trong mot doan mach dien xoay chieu khong phan nhanh, ciTong do ddng dien tre pha so v6i hieu dien the giffa hai dau doan mach, t h i doan mach nay gom dien t r d thuan va cupn cam. Vay chon dap an B. 10 GiSi Chi titft f = — = 6,038.10"HZ. h Vdy chgn dap an A. Cdu 26: M o t k h u n g d a y d a n h i n h chOr n h a t c6 100 vong, d i e n t i c h moi vong 600 cm^, quay deu quanh true doi xufng cua k h u n g vdfi v a n toe goe 120 vong/phut t r o n g m o t tCf truf&ng deu eo cam ufng ttf bang 0,2T. True quay vuong goe v d i cac dUorng cam ufng tCr. Chon goe thori gian la lue vectof phap t u y e n cua m a t phSng k h u n g d a y ngUtfc hifdfng vdfi vector cam ufng tii. B i e u thufc suat d i e n dong cam ufng t r o n g k h u n g l a : A . e = 4,8;isin 4 0 ; r t - - ( V ) . 2 C. e = 4871 B. e = 487tsin(4;rt + n ) ( V ) . sin 4 0 7 r t - - ( V ) . 2 D. e = 4,87isin(407rt + 7 i ) ( V ) . Giai Theo de b a i , t a c6: + D i e n t i c h v o n g day: S = 600cm^ = 6.10"^m^ + So v o n g day: N = 100 vong. •f C a m ufng tCr: B = 0,2T. + Tdc do quay cua roto: 120 vong/phut = 2 vong/giay. Vao thcfi d i e m t = 0, goe giffa phap t u y e n cua k h u n g day va cam ufng tff l a a = 71. Ta C O tCf t h o n g qua m o t vong day l a : cp, = BScos(a + 7r) = BScos(27rnt + 7r). V i k h u n g day c6 N vong giong nhau n e n t r o n g k h u n g c6 suat dien dong: e = - ^ = NBS27msin(27mt + 7 r ) . N T h a y so t a c6: e = 4,87isin(407rt + 7 i ) ( V ) . Vdy chgn dap an D. 12 Giai Chi ti^t dS thi T S DH, C D M6n V^t If Cdu 27: T r o n g t h i n g h i e m giao thoa a n h sang vdfi khe l a n g (Y-ang), khoang each giffa h a i khe la 2 m m , khoang each tii m a t p h a n g chufa hai khe den m a n quan sat la 1,2 m. Chieu sang h a i khe b a n g a n h sang hon hop gom h a i a n h sang dcfn sSc c6 badfc song 500 n m va 660 n m thi thu diXac h§ v a n giao tlioa t r e n m a n . B i e t v a n sang ehinh giUa (trung tarn) ufng vdri h a i bufe xa t r e n t r u n g nhau. K h o a n g each tii v a n chinh giffa den v a n gan n h a t cung mau v d i v a n c h i n h giufa l a : A. 9,9 m m . B. 19,8 m m . C. 29,7 m m . D. 4,9 m m . Giai T a c6: vdri X. = 500nm t h i i , = a = 0,3mm. vdri ^2 = 660nm t h i k i i i = k2i2 = - ^ = 0,396mm. a k| _ i , _ 396 _ 33 k^ " i j ~ 300 " 2 5 ' Gia t r i nguyen nho n h a t la k i = 33, k2 = 25. Khoang each tii v a n ehinh giffa den v a n gan n h a t cung m a u vdfi v a n ehinh giffa l a : 33.0,3 = 9,9mm. Vay chqn dap an A. Cdu 28: M o t con lac 16 xo gom 16 xo eo do eijfng 20 N / m va v i e n b i c6 kho'i lirgrng 0,2 k g dao dong dieu hoa. T a i t h 6 i d i e m t , v a n to'c va gia toe eua v i e n b i I a n li/gtt l a 20 cm/s va 23 m/s^. B i e n do dao dong cua vien b i l a : A. 4 em. B. 16 em. C. 10 V3 em. D. 4 V 3 cm. Giai A p dung d i n h l u a t bao toan nang iLfgrng, t a c6: i k A ^ = - k x ^ + - m v ^ =-!-kx^ +-\w' 2 2 2 2 2co' Thay cAc gia t r i co - => A = . V CO — = 10(rad/s), v = 20(cm/s), a = -co^x vao bieu m thdre t r e n t a di/dc A = 4cm. Vdy chgn dap an A. Cdu 29: M o t con l^c 16 xo treo thSng dufng. K i c h t h i e h cho con l^c dao dong dieu hoa theo phiTOng t h a n g dufng. Chu k i va b i e n do dao dong GiaiChitiStdSthiTSDH, CDM6nVatli • • 13 cua con He I a n lifOt l a 0,4 s va 8 cm. Chon true x'x t h i n g duTng chieu ducrng hifdng xuong, goc t o a do t a i v i t r i can b k n g , goc t h 6 i gian t = 0 k h i v a t qua v i t r i c a n b ^ n g theo c h i e u difdng. L a y g i a to'c r o i tii do g = 10 m/s^ v ^ 7t^ = 10. Thori gian ng^n n h a t ke tijf k h i t = 0 den k h i ILTC d a n h o i cua 16 xo c6 do I6n ale t i e u l a : A. ^ s . 30 B. ±s. 15 C. Is. D. 10 -s. 30 GiSi Chu k i : T = 2% CO = STC. CO K h i treo v a t vko, 16 xo g i a n m o t doan: A / = — g = = 0,04m < A = 0,08m. k CO LLTC d^n h o i cua 16 xo c6 do l 0 t a c6 phuomg t r i n h dao dong: X = 8 sin 57rt => 8 sin 57rt = - 4 sin 57rt =-0,5 57rt = - — + 2 k 7 t 6 Vdy chon dap an A. Cdu 30: D a t vao h a i dau doan mach dien R L C k h o n g p h a n n h a n h m o t hieu d i e n t h e u = 220V2cos c o t - i ^ ( V ) t h i C L r 6 n g do d6ng dien qua 2 doan mach c6 bieu thiJc l a i = l-Jlcos 4 ( A ) . Cong sua't tieu t h u cua doan mach n a y l a : A. 2 2 0 V 2 W . B. 440W. C. 4 4 0 V 2 W . D . 220 W . G\k\ Dp lech pha giuTa ciTdng do dong di^rt v a h i e u dien t h e : V2 ^2 n ^ 4 14 Giai chi.tigf 66 thi TS DH, CD M6n VHt II Cong suat t i e u t i i u cua doan mach: P = U I cos

Z, = R V3. 3 Ta c6: Uc = V3 Ud ^ IZ^ = yfz.l^R'+3Zl = V 3 . W R ' + 3 R ' = 1.2^.R =^ Zc = 2 V 3 . R Do lech pha giffa u va i : tan(p= Z L - Z C = N/3R-2V'3R r- 71 = _V3=>cp = - y . Do lech pha cua hieu dien the giCifa hai dau cuon day so vdfi hieu dien the giCifa hai dau doan mach tren la: 71 271 3 Vdy chon dap an A. Cdu 34: Trong mach dao dong LC c6 dao dong dien tCr tiT do (dao dong rieng) vdfi tan so goc lO"* rad/s. Dien tich dai tren tu dien la lO'^C. CLTC Khi cUofng do dong dien trong mach bkng 6.10"^ A t h i dien tich tren tu dien la: A. 4.10"^°C. B. 6.10"^°C. C. 2.10-^°C. 16 . - D. 8.10-^°C. QiaichitigtdethiTSDH, CBMSn vatli Theo d i n h luat bao toan nSng lucfng, t a c6: 2 - +2C— cu^ =- q = ^ C ' U ^ - C L i ' =8.10-'° (C). Vdy chgn dap an D. Cdu 35: H a t n h a n ^^gRa bien ddi t h a n h h a t n h a n ^g^R" do p h o n g xa: A. p \. a va p " . C. a . Ta CO phircJng t r i n h : -fgRa ^ . D. p". 'g^Rn+ 2He. ^He la h a t a. Vdy chgn dap an C. Cdu 36: M o t c h a t d i e m dao d o n g d i e u h o a X = 3sin 6J theo phiTcfng t r i n h (x t i n h bang cm va t t i n h b ^ n g giay). T r o n g m o t giay dau t i e n tCr thcfi d i e m t = 0, chat d i e m d i qua v i t r i c6 l i do x = + 1cm: A. 4 I a n . B. 7 I a n . C. 5 I a n . D. 6 Ian. , GiSi Chu k i dao dong: T = — = 0,4s. N g h i a la t r o n g I s , v a t thufc h i e n CO 2,5 chu I d . T r o n g m o t chu k i , v a t d i qua v i t r i c6 U do x = + l c m h a i l l n nen t r o n g I s , v a t d i qua v i t r i c6 l i do x = + l c m n a m I a n . Vdy chgn dap an C. Cdu 37: M o t song ccf Ian t r u y e n t r e n m o t dLforng t h i n g tii d i e m O den diem M each O m o t doan d. B i e t t a n so f, budc song X vk b i e n do a cua song k h o n g doi t r o n g qua t r i n h song t r u y e n . N e u phi/cfng t r i n h dao dong cua p h i n tuT v a t chat t a i d i e m M c6 dang UM(t) = asin27tft t h i phifofng t r i n h dao dpng cua p h a n tuT v a t chat t a i O 1^: A. U o ( t ) = asinjr B. U o ( t ) = asin;c C. U o ( t ) = asin23i D. U o ( t ) = asin2;i ft4 Neu phifcfng t r i n h dao dong cua p h a n tijf v a t chat t a i d i e m M c6 # d dang U M ( t ) = a sin Inft t h i t h d i gian t r u y e n song tCf O d§n M 1^ At = —. Gt&i Chi ti^t d l thi TS OH. CD M6n V$t II I 17 Khi do dao dong tai O sdm pha hon tai M la 27rd . Phi/ong t r i n h dao dong cua phan tuf vat chat tai O la: Uo(t) = asin27r Vdy chqn dap an C. Cdu 38: K h i c6 hien ttfcrng quang dien xay ra trong te bao quang dien, ph6t bieu nao sau day la sai? A. Giuf nguyen cLforng do chum sAng kich thich va k i m loai dung lam catot, giam tan so cua anh sang kich thich t h i dong nang ban dau C L T C dai cua electron (electron) quang dien giam. B. GiCr nguyen chum sang kich thich, thay ddi k i m loai lam catot thi dong nang ban dau ciTc dai cua electron (electron) quang dien thay doi. C. Giuf nguyen t a n so cua anh sang kich thich va kim loai lam catot, tang cifcfng do chum sang kich thich t h i dong nang ban dau c\Xc dai cua electron (electron) quang dien tSng. D. Giu" nguyen ctfcfng do chum sang kich thich va kim loai dung lam catot, giam hiidc song cua anh sang kich thich t h i dong nSng ban dau CLfc dai cua electron (electron) quang dien tang. Giai Theo dinh luat quang dien, khi c6 hien tiigrng quang dien xay ra trong te bao quang di?n, dong nang ban dau ciic dai ciia cac quang electron hoan toan khong phu thuoc vao ciicfng do anh sang kich thich ma chi phu thuoc vao budfc song va tan so. Vdy chgn dap an C. Cdu 39: Tai hai diem A va B trong mot moi tri/dng truyen song c6 hai nguon song ket hop, dao dong cung phtrong vdri phifcfng trinh Ian lifc*t la UA = asincot va U B = asin((ot + 7 i ) . Biet van toe va bien do song do m5i nguon tao ra khong doi trong qua trinh song truyen. Trong khoang giuTa A va B CO giao thoa song do hai nguon tren gay ra. Phan tuf vat chat tai trung diem cua doan AB dao dong vdfi bien do bkng: A. - . B. 2a. C. 0. D. a. 2 18 GiSi Chi tigt thi TS D H , C D M6n VSt!( Giai T a i t r u n g diem dao dong eua h a i nguon t r u y e n tori ngi/gfc pha nhau nen bietn dp dao dong t o n g hgfp bSng 0. Vay chgn dap an C. . Cdu 40: P h a t bieu nao sau day la dung k h i n o i ve dong d i e n xoay chieu ba pha? A. K h i cifcfng do dong dien t r o n g m o t pha b k n g k h o n g t h i cifdng do dong dien t r o n g h a i pha con l a i khac k h o n g . B. Chi C O dong dien xoay chieu ba pha m d i tao diic/c tCf tn/c/ng quay. C. K h i ciidng do dong dien t r o n g m o t pha ctfc d a i t h i ci/cfng do dong dien t r o n g h a i pha con l a i ctfc tieu. D. Dong dien xoay chieu ba pha la h e t h o n g gom ba dong dien xoay chieu m o t pha, lech pha nhau goc 2n —. Giai Dong dien xoay chieu ba pha la he t h o n g gom ba dong d i e n xoay chieu m o t pha, lech pha nhau goc Vay chon dap an D. Cdu 41: Neu chum t i a sang 16 k h o i t h a u k i n h p h a n k y ma h o i t u t a i mot diem t h i chum t i a td\u k i n h do c6 diTdng keo d a i : A. giao nhau cf sau t h a u k i n h va giao d i e m each t h a u k i n h m o t khoang nho h o n do Idrn t i e u C L T cua t h a u k i n h . B. giao nhau d sau t h a u k i n h va giao d i e m each t h a u k i n h m o t khoang Idfn hon do Idfn t i e u C L T cua t h a u k i n h . C. giao nhau of sau t h a u k i n h va giao diem t r u n g vdri t i e u d i e m v a t cua t h a u k i n h . D. song song vdfi true c h i n h cua t h a u k i n h . Giai Neu chum t i a sang 16 k h o i t h a u k i n h p h a n k y m a h o i t u t a i m o t diem t h i chum t i a t 6 i t h a u k i n h d6 c6 dudng keo d a i giao nhau 6 sau thau k i n h va giao diem each t h a u k i n h m o t khoang nho hOn do 16n tieu C U T ciia t h a u k i n h . Vay chgn dap an A. Giai Chi tietde thi TS D H , C D Mon Vat li , ' 19

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