PHAN HAI QUANG HINH HOC Mot hien tuong quang hoc : Cau My Thuan soi bong tren song Tien Anh sang la doi tupng nghien cuu ciia Quang hpc Quang hinh hpc la phdn Quang hpc nghien ciiu sy truyen anh sang qua cac mdi trudng sudt, va nghien ciiu sy tao anh bdng phuong phap hinh hpc Nhd cac nghien ciiu ve Quang hinh hpc, ngudi ta da che tao nhieu dyng cy quang can thiei cho khoa hpc va ddi sdng 159 QUANG HINH HOC Khucxaanh sang Mat Cac dung cu quang 160 CHUONG VI Khuc xa anh sang Cac chum tia sang mot le hoi dem Anh mpt cai thuoc nhiing nuoc Ba dinh luat co ban ciia Quang hinh hpc la : • Oinh luat truyen thdng anh sang ; - Ojnh luat phan xa anh sang ; - Dinh luat khiic xa anh sang THCS, ta da khao sat so bp ve cdc dinh luat ciing vdi mpt sd img dyng ciia guong phang, guong cau, thau kinh, mdt, Khiic xa anh sang la hien tupng quan cd nhieu iing dung Trong chuong chiing ta se nghien ciiu day dij hon ve su khiic xa, ddng thdi tim hieu them mpt hien tupng cd lien quan : hien tupng phan xa toan phan 11-VATLI 11.(C)-A m Cap quang dijng Y hgc 161 KHUC XA ANH SANG O ldp 9, ta da buac dau tim hieu hien tupng khuc xa anh sang ve mat dinh tfnh Trong bai hpc sau day, chung ta se khao sat ddy du hon hien tupng ve mat dinh luong tiinn ^6.1 Do hien tupng khiic xa anh sang, ta thay thia coc nhu bi gay mat nuoc Xnen (Willebrord Snell) giao su toan va vat li tai Dai hpc Lay-den (Leyden), ngudi da kham pha dinh luat khiic xa anh sang dong thdi vdi De-cac (Descartes) I - SI/ KHUC XA ANH SANG Hien tifcrng khiic xa anh sang Khuc xq dnh sdng Id hien tugng lech phuang (gdy) eiia cdc tia sdng truyen xien gdc qua mat phdn cdch giiia hai mdi trudng sudt khde Djnh luat khuc xa anh sang Hinh 26.2, ta ggi : , SI : tia tdi ; / : diem tdi ; N'lN : phdp tuyen vdi mat phan cdch tai / ; , IR : tia khiic xa ; , i : gdc tdi ; /• : gdc khiic xa 11-VATLM1.(C)-B Khi thay ddi gdc tdi i, thue nghiem cho ket qud sau day, dugc ggi la dinh luat khiic xa dnh sdng : - Tia khue xq ndm mat phdng tdi (tqo bdi tia tdi vd phdp tuyen) vd a phia ben phdp tuyen so vdi tia tdi - Vdi hai mdi trudng sudt nhdt dinh, ti sd giua sin gdc tdi (sini) vd sin gdc khuc xq (sinr) ludn khdng ddi : sini sinr Thuoc do = hang sd (26.1) Oen chieu t laze II - CHIET SUAT CUA MOI TRUOfNG Chiet suat ti doi Khoi nhira ban tru suot sinr Ti sd khdng doi —^— hien tugng khiic xa sinr duge ggi Id chidt sudt n ddi «,, ciia mdi trudng (2), (chira tia khiic xa) ddi vdi moi uudng (1) (ehira tia tdi): sini sinr = "21 Hinh 26.3 Dung cu cac goc /' va rde nghiem lai dinh luat khiic xa anh sang (26.2) •Ne'u «2i > thi r < i Tia khiic xa bi lech lai gdn phdp tuyen hon Ta ndi moi trudng (2) chidt quang /!0'/7 mdi trudng (1) - Neu «T, < thi r > i: Tia khiic xa bi lech xa phdp tuyen han Moi trudng (2) chidt quang kem moi trudng (1) Chiet suat tuyet ddi Chief sudt tuyet ddi (thudng gpi tdt la chiet sudt) eiia mot mdi trudng Id chiet sudt ti ddi cua mdi trudng dd ddi vcfi chdn khdng Nhu vay, chiet sua't eiia chan khdng Id Chiet suai eua khong khf Id 1,000293 (rat gdn vdi chiet suat eiia chan khong) nen thudng dugc tfnh trdn Id 1, neu khong cdn chfnh xac cao Bang 26.1 Kei qua goc toi / va goc khuc xa r tuong ung thi nghiem Hinh 26.3 '• sin/ Sinr 0° ' 0° 0 j 10° 6,5° 0,174 0,113 20° 13° 0,342 0,225 30° 19,5° 0,500 0,334 40° 25,5° 0,643 0,431 50° 31° 0,766 0,515 60° 35° 0,866 0,574 70° 39° 0,940 0,629 80° 41,5° 0,985 0,663 163 Mgi moi trudng sud't deu cd chiet sua't tuyet ddi Idn ban Cd the thie't lap dugc he thiic : «21 = «2 «1 '-' 20° 40° 60° 80° 100°/ Hinh 26.4 Do thi bieu di§n su phu thuoc cua goc r vao gdc i theo Bang 26.1 (26.3) dd : «2 Id chiet sudt (tuyet ddi) ciia mdi trudng (2); «, la chiet suat (tuyet ddi) ciia mdi trudng (1) vay edng thiie ciia dinh luat khiic xa cd the viet theo dang ddi xiing : Hu ; E ; B J njsini = niSinr O 0,2 0,4 0,6 0,8 (26.4) Sin; Hmh 26.5 Do thi bieu dien su phu thuoc ciia sinr vao sini theo Bang 26.1 III - TINH THUAN NGHJCH CUA SU TRUYEN ANH SANG M l Viet cdng thirc cua dinh luat khiic xa vdi cac gdc nho (< 10°) Thf nghiem cho thay : O Hinh 26.2, ne'u dao ehidu, cho anh sang truyen tir nude khdng theo tia RI thi nd khiic xa vao khdng khf theo tia IS Nhu vay, dnh sdng truyen di theo dudng ndo thi ciing truyen nguge lai theo dudng dd *3fA Ap dung dinh luat khuc xa cho trudng hop / = 0°- Ket luan Day la tinh thuan nghich ciia su truydn anh sang Tir tfnh thuan nghich, ta suy ; 1*5 Hay ap dung cdng thdc ciia dinh luat khuc xa cho sU khuc xa lien tiep vao nhieu mdi trudng cd chiet suat lan lugt la n.,, Hg. - "n va cd cac mat phan each song song vdi Nhan xet 164 « i = : ^21 (26.5) Tfnh thuan nghich cung bieu hien d sU truyen thdng va su phdn xa Bdi tap vi du Tia sang truydn tir mot chat sudt co chiet suat /( tdi mat phan each vdi moi trudng khdng Goe khuc xa khong khf la 60° Tia phan xa d mat phan each co phuotig vuong gdc vdi tia khuc xa (Hinh 26.6) Tfnh chiet suat /; Gidi Theo di bai : / ' + ;• = 90" Ta suy : / + r = 90" Ap dung dinh luat khuc xa : iisini = sinr sin;Tir : // = sin/ VI sin/ = cosr nen : /( = tanr Gill cIni : Nguyen nhan ciia hien tuang khuc xa la su thay ddi tde truygn anh sang Ngudi ta thie't lap duoc he thire v^ chiet suat tuyet ddi n ciia mot moi trudng nhu sau : c Thay sd, ta dugc : n = tan 60" = V? = 1.73 ll = — Bang 26.2 Chiet suat ciia mpt so moi trudng'^I I Chat rdn (20°C) Chiet suat : Chat rdn (20°C) Chiet suat Muoi an (NaCI) 1,544 Ho phach 1,546 Polistiren 1,590 Xaphia 1,768 Chat long (20°C) Chiet suat Rupu etilic 1,361 Glixerol 1,473 u I i Kim cuong 2,419 I Thuy tinh crao 1,464 ^ 1,532 i Thuy tinh flin 1,603-^1,865 Nuoc da Chat long (20°C) Nuoc Benzen Chat man ^ , ^ (0°C; atm) Khong u (• ia toe anh sang chan khdng ; ll la tde anh sang moi trudng 1,309 Chiet suat ' 1,333 1,501 „,.- -, Chiet suat 1,000293 Chat (0°C ; atm) Khi cacbonic Chiet suat 1,00045 Djnh luat khuc xa anh sang : — Tia khuc xa nam mat phang tdi va or phia ben phap tuyen so v6i tia tdi — Vdi hai moi trUdng suot nhat dinh, ti so giUa sin goc tdi (sin/) va sin goc khiic xa (sinr) luon khong d o i : smi = hang sd smr (1) Xac dinh vdi anh sang vang natri phat (xem bai Lang kinli) 165 ,"*!-; Chiet suat: # ' • " , • , sin/ — Chiet suat ti d d i : n,, = sinr — Chiet sua't tuyet d o i : ' i '-,1 + Chiet suait ti ddi ddi vdi chan khdng 4& + Ta co : n,., = — "2 "1 Cdng thUc cua dinh luat khuc xa anh sang viet dUdi dang ddi xUng : n^sin/ = n^sinr CAU HOI VA BAI TAP A Tia Sd1 The nao la hien tuong khuc xa anh sang ? Phat bieu dinh luat khiic xa anh sang Chiet suat ti doi n^^ ciia moi truong (2) doi voi moi trudng (1) la gi ? Chiet suat (tuyet doi) n ciia mpt moi trudng la gi ? Viet he thiic lien he giua chiei suat ti doi va chiet suat tuyet doi The nao la tinh thuan nghich ciia su truyen anh sang ? Chung to ; ni2 '21 B Tia S^ C Tia S3/ D Sd ; S^I ; S3/ deu cd the la tia tdi Tia sang Hinh 26.7 truyen tii nude va khuc xa khdng Tia khiic xa va tia phan xa d mat nude vudng gdc vdi Nude cd chiet suat la - • Gdc tdi cua tia sang la bao nhieu (tinh trdn so) ? A 37° B 42° C 53° Nuoc CO chiei suat la - Chiet suat ciia khong D Mdt gia tri khac A, B, C doi voi nude la bao nhieu ? Cd ba mdi trudng sudt t , ? , ^3" Vol cung gdc toi;, mpt tia sang khiic xa nhu Hinh 26.8 truyen tit ^ vao vatu vao ^, Mpt tia sang truyen den mat thoang ciia nude Tia cho mpt tia phan xa d mat thoang va mpt tia khuc xa Ngudi ve cac tia sang quen ghi lai chieu Injyen Hinh 26.7 Tia nao dudi day la tia tdi ? Hinh 26.8 166 Van vdi gdc toi /, tia sang truyen ti; vao -1- thi gdc khiic xa la bao nhieu (tinh trdn sd) ? A 22° B 31° C 38° D Khdng tinh dupe, vi thieu yeu td Mdt tia sang dupe chieu den diem giua ciia mat tren mdt khdi lap phuong sudt, chiet suat n = 1,50 (Hinh 26.9) Tim gdc tdi / Idn nhat de tia khuc xa vao khdi cdn gap mat day ciia khdi Mdt cai thude dupe cam thdng dung vao binh nude cd day phdng, ngang Phan thude nhd khoi mat nude la cm Chech d tren cd mdt ngpn den Bong ciia thude tren mat nude dai cm va d day dai cm / ^ ^ / / Tinh chieu sau ciia nude binh Chiet • suat cua nuoc la TT Hmh 26.9 Em CO biet ? SL/TAO ANH QUA LUONG CHAT PHANG Trong dai song, ta thuong gap truong hgp nhin anh cua mot vat khuc xa anh sang ma co, chdng han nhu nhin mot ca bai loi h6 nuac, nhin hon soi a day suoi, (Hinh 26.10) Khi do, anh sang da khuc xa qua mat phdng phan each hai moi truong suot He hai moi truong tao mot kr&ng chat phing Anh cua vat dugc tao bai mot chiim tia sang rat hep di vao mSt Neu quan sat theo phuang vuong goc vai mat phdng phan each, ta co the thiet lap dugc cong thirc xac dinh vi tri anh (cong thiJc ciia luang chat phdng) Hmh 26.10 Ban the nao de mui ten triing ca ? That vay, theo Hinh 26.11, ta co : HI = /-/S2tanr= HS.sinr HS.Xani = /^5,sin/ HS^ Dodo HS HS^ sin/ sinr / n^ HS^ Vay Neu nhin tir khong vao nuac thi '^ Do HS,= | / ^ S , n,2 = 1• ;' n - Ii = ^3 - L^wMw,,-.2 Anh dugc "nang" len gan mat nuac so vai vat ® H (26.6) •r / ly © S, ,-' y ' Si / Hir}h 26.11 167 PHAN XA TOAN PHAN Ngay nay, mpi nguai d^u nghe noi den cap quang diing Cong nghe thong tin, Y hoc, Hien tuong c a ban dugc ap dung cap quang la phan xa toan phan Phan xa toan phSn la gi ? Chum tia laze Tia phan xa I - SLT T R U Y E N A N H SANG V A O M O I TRl/OfNG CHIET Q U A N G KEM H O N («, > nd Tia khuc xa Hinh 27.1 l T h i nghiem CT Tai d mat cong ciia ban tru, chiim tia tdi hep truyen theo phcrcing ban kinh lai taiyen thing ? Ta cho mot chiim tia sang hep truySn tir khoi nhira suot hinh bdn tm vdo Ichong khf v6i cdc diing cii bo trf theo so d6 a Hinh 27.1 CT P P Van dung tinh thuan nghich cua su" truyen anh sang, hay neu cac ket qua anh sang truyen vao moi trudng chiet quang han Thay d6i nghieng cua chdm tia toi (thay doi goc toi /) vd quan sdt chum tia khiic xa khong khf K^ Kdt qud : Gdc tdi • Nho • Co gia tri dac biet / f, Chiim tia khiic xa • Lech xa phap tuyen (so vdi tia tdi) • Rat sang • Gan nhu sat mat phan each • Rat md • Co gia tri lon hon gia tri i^^ 168 Chiim tia phan xa Khdng • Rat mo • Rat sang i • Rat sang CAU HOI VA BAI TAP 1^: Neu cong dung va cau tao ciia kinh thien van Ve dudng truyen ciia chiim tia sdng qua kinh thien van ngam chung d vo cue, Hay chon dap an dung cac bai tap va dudi day So boi giac ciia kinh thien van ngdm chung Viet cong thuc ve so boi giac ciia kinh thien van ngdm chung vo cue, vo eye CO bieu thiic nao ? A.® B d ) Giai thich tai tieu cy vat kinh cua kinh thien van phai Ion C 'S , D, Bieu thiic khac Khoang each giua vat kinh va thi kinh cua kinh thien van ngdm chiing d vo eye co bieu thiic nao ? Dat f., va ^2 lan lugt la tieu cy ciia vat kinh va A ® B @ , thi kinh ciia kinh thien van C @ D Bieu thiic khac Xet cac bieu thiic: Vat kinh ciia mpt kinh thien van diing trudng hoc CO tieu cu f^ = 1,2 m Thi kinh la mpt thau f,,f, kinh hoi tu co tieu cy fg = cm m^ ^1 fl Tinh khoang each giua hai kinh va sd boi giac ciia kinh thien van ngam chiing vo eye Em CO biet ? TU KINH THIEN VAN CUA GA-LI-LE OEN KINH THIEN VAN HOP-BON '1* Ga-li-le la nguai dau tien co y tuang dung kinh thien van'^' Lip-pa-si (Hans Lippershey) a Ha Lan phat minh vao nam 608 (ban dau gpi la "kinh tham tir" : spyglass) vao viec quan sat bdu trai Chfnh ong da tu che tao chiec kinh thien van cd so boi giac khoang 30 va hien dugc luu giu tai Vien bao tang Flo-rang-xa Dung kinh nay, Ga-li-le da cd nhieu kham pha quan ve Thai Duang he Day la loai kmh thien van khuc xa diing thau kinh hoi tu lam vat kfnh Hmh 34.6 Kinh thien van l-ec-xd (1) Kfnh duoe dat theo ten cila nha thien van MI Hdp-bon ngudi da phat hien quy luat \i chuygn dong ciia cac thien mang ten dng (2) Ta thudng hieiu kfnh viSn vong la kfnh diing da quan sat cac vat d xa tren mat dat cdn kfnh thien van la kfnh diing de quan sat cac thien tht Hai loai kfnh deu cd cung nguyen If cau tao gdm vat kfnh (la tha'u kfnh hoi tu hay mot guong cdu 1dm) va thi kfnh 216 Cho tai nay, kfnh thien van Idn nhat thuoc loai la kfnh cua Oaf thien van l-ec-xo (Mi) Kfnh CO tieu cu 19,8 m va vat kfnh co dudng kfnh be mat la 1,02 m Che tao cac kfnh thfen van khuc xa Ion rai phuc tap va kho khan Viec che tao cac thau kfnh CO be mat lan ddi hoi chai lieu thuy tinh phai tinh khiei, lam nguoi phai that cham va cau true ca hoc phai that vung chdc Du vay, theo thdi gian, thau kfnh lam vat kfnh van bi bien dang (do thuy tinh la chat vo dinh hinh) anh hudng den sytao anh VI nhung If neu tren ma vd sau cac kfnh thien van ddu thuoc loai phan xa, vat kfnh la mpt guong parabol Loai kfnh thien van dugc Niu-ton phat minh va su dung dau tien vao nam 1672, dugc gpi la kfnh viSn vong Hien nay, kfnh thien van phan xa Idn nhai la kfnh thien van Kech cua Dai thien van Mao-na Ki dat tai Ha-oai, co dudng kfnh be mat 10 m -•«'*" Hinh 34.7 Kinh thien van Niu-tdn Hmh 34.8 Anh ehup thien Tien Nu (Andromeda) cach Trai Dat 900 000 nam anh sang qua kinh thien van Tuy nhien, viec quan sat bau trdi tir cac kinh thien van dat tren mat dat deu bi tra ngai bdi bau khf quyen Ngoai su can trd cac hien tugng thdi tiet (mua, bao ) thi su khuc xa cua anh sang truydn vao bau khf quyen cung anh hudng den sutao anh Oe khde phuc nhugc diem nay, vao 24-4-1990, CO quan NASA da phdng vao khdng gian kinh thien van l-iap-bon bay quanh Trai Oat Nhd boat dpng d ngoai bau khf quyen va su dung cac thfei bi hien dai nhai ve quang hpc va vidn thong, kfnh thien van Hdp-bon la cdng cu tinh vi nhat giup ngudi thu nhan dugc thong tin td nhung vat the rai xa xam cua vu try Cd the tim dgc them ve kfnh Hdp-bon d dia chf : http://www.hubblesite.com Hinh 34.9 Kinh thien van Hdp-bdn 217 35 Thac hanh : X A C OINH TIEU Cl/ CUA THAU KINH PHAN Ki Thau kfnh phan kl chf tao anh ao cua vat that vdi moi khoang each c/tCr vat den thau kfnh VI khdng the dugc anh ao tren man anh, nen khdng biei chfnh xac vi trf cua anh ao va dd khdng dugc khoang each Id 'I tu anh ao de'n thau kfnh Vay cd each nao xac dinh dugc tieu cu fcua thau kfnh phan kl khdng ? I-MUC DICH THI NGHIEM Biet dirgfc phirofng phap xac dinh tieu cir ciia thdu kfnh phan ki bdng cdch ghep no dong tnac vdi mot thdu kfnh hoi tii de tao dnh that ciia vat that qua he hai thdu kfnh Ren luyen ki nang sir dirng gid quang hoc de xac dinh tieu cir ciia thau kfnh phan ki II-DUNG CU THI NGHIEM Bo thiet bi thf nghiem "Xac dinh tieu cir cua thdu kfnh phan ki" duoc bd trf nhu Hinh 35.la Hmh 35.1a 218 • Gia quang hoc G, co thude ddi 75 cm Den chieu D, loai 12 V - 21 W Ban chdn sdng C, mau den, tren mat co mot 16 tron mang hinh sd dung lam vat AB (Hinh 35.1b) Thau kfnh phan ki L Thau kinh hoi tu LQ Hinh 35.1b Ban man anh M Ngudn dien U (AC - DC : 0-3-9-12V/3A) Bo hai day ddn co ddu phich cdm III-COfSdLf THUYET Dat mot vat that AB vuong goc vdd triic chfnh ctia mot thau kfnh phan ki L Vi thau kfnh phan ki luon tao mot dnh A'B' vdi moi khoang each d tir vat AB den thdu kfnh, nen khdng biet chinh xac vi trf dnh ao A'B' Do ta khong trirc tie'p duoc khoang each \d'\ tir dnh den thau kfnh vd khong xac dinh duoc tieu cir/cua thdu kfnh phan ki L theo cdng thtic : f=^^, d + d' m Hay neu rd : - tfnh chat cua anh ao A'B' tao bdi tha'u kfnh phan ki doi vdi vat that AB - quy irdc ve dau dai sd ciia cac dai lu'dng d, d', f cdng thdc (35.1)' (35.1) HI De khde phiic kho khan neu tren, ta cd the dp diing phuong phdp sau day : a) - Dat vat AB tai vi trf (1) trudc thau kfnh hoi tu LQ de thu duoc mot anh that A'B' ro net nhat tren man dnh M (Hinh 35.2a) Sau do, giii cd dinh vi tri ciia thdu kfnh LQ va man dnh M - Ghep thau kfnh phan ki L dong tnrc vdi thdu kfnh hoi m LQ he thau kfnh (L, LQ) Di chuyen vat AB toi vi tri (2) cho anh A'^B'^ tao boi thau kfnh phan ki L dugfc coi la vat that ddi vdi thau kinh hoi tii LQ va thdu kfnh LQ lai tao mot dnh that A.!^^ ro net nhat tren man anh M Khi d6 vi trf cua anh AJBJ trung vdi vi tri (1) cda vat AB (Hinh 35.2b) b) Hmh 35.2 219 Nhu vay, ne'u khoang each d tix vi trf (2) ciia vat AB va khoang cdch \d'\ tit vi tri (1) ciia vat den thau kinh phan ki L, ta se xde dinh duoc tieu cu /ciia tha'u kfnh phan ki L theo cong thdc (35.1) IV - GlCri THIEU DUNG CU DO Gid quang hoc G (Hinh 35.3) la mot mang truot bdng hop kim nhom, ddi 75 cm, dat ndm ngang Tren than gid G co mot thude milimet T, dung xac dinh vi trf ciia vat AB, ciia cdc thdu kfnh L, LQ vd man dnh M gdn tren gid G nhd cdc vft ham Mot den chieu D (loai 12 V - 21 W) co kfnh tu quang, dung lam ngudn sang va dugfc cap dien bdi ngudn dien U (AC - DC : 0-3-9-12V/3A) Mudn thay doi vi trf ciia vat AB, ciia cac thau kfnh L LQ vd cua man dnh M tren gid quang hoc G, ta chi cdn ndi long cac vft ham vd dich chuyen chung trucrt tren gid ndy u ^3SP Hinh 35.3 V - TIEN HANH THI NGHIEM Cdm phfch lay dien cua den chieu D vao hai 16 cdm cap dien xoay chieu (ghi dau ~ ) ciia ngudn dien U Van num xoay cua nguon dien den vi tri 12 V va bat cdng tde cua nd de den chieu D phdt sdng Dat vat AB, tha'u kfnh hgi tu LQ vd man dnh M (theo thu tir nay) len gia quang hgc G, vudng goc vdi chifiu ddi cua gid : 220 - Vat AB d tai vi tri (1), each den chieu D khodng 10 H- 15 cm Ghi vi trf (1) cua vat AB vdo Bdng thuc hanh ; - Thau kfnh hgi ttr LQ vd man dnh M a gdn sdt phfa sau vat AB Didu chinh den D cho vdng trdn sdng nd phdt chieu vira kfn mat 16 tron chua vat AB vd truyen qua viing chfnh giiia mat thdu kfnh LQ C E Dua vao dieu kien tao anh tnat cua thau kfnh hoi tu ddi vdi vat that de phdi hgfp dich chuyen tha'u kinh hgi tu LQ vd man anh M xa dan vat AB cho tdi thu dugfc dnh that A'B', Idn han vdt, hien rd net nhdt tren man anh M I ^ Mudn tha'u kfnh hdi tu LQ tao anh that A'B' Idn hon vat that AB (Hinh 35.2a), ta can phai chon cac khoang each td vat AB va td man anh M den thau kfnh hdi tu LQ thoa man dieu kien gi so vdi tieu cU cua tha'u kfnh ? GiG CO dinh vi trf cua thdu kfnh hdi tu LQ vd man dnh M Dich vat AB rdi xa thdu kfnh hgi tii LQ them cm, den vi trf (2) Dat thdu kfnh phan ki L vao khoang giiia vat AB va thau kfnh hgi tii LQ, ghep thdnh mgt he hai thdu kfnh dong true (L, LQ) tren gid quang hgc G Dua vao didu kien tao anh ciia thdu kfnh phan ki ddi vdi vat that de dich chuyen tha'u kinh phan ki L cho tdi thu dugc dnh thdtA'.,B'^, nhd hem vdtAB tf\ Mudn anh cudi cung ciia vat vd hien rd net nhdt tren mdn dnh M f E Ghi vao Bang thirc hanh 35.1 gid tri cua : - khoang cdch d tir vi trf (2) cua vat AB den thau kinh phan ki L ; - khoang cdch \d'\ tir vi tri (1) cua vat AB den thdu kfnh phan ki L AB tao bdi he thau kinh (L, LQ) bd tn nhu- Hinh 35.2 la anh that, thi khoang each gida thau kfnh phan kl L va tha'u kfnh hdi tu LQ phai Idn hon hay nho hon tieu ciT ctia thau kfnh hoi tu LQ ? Giai thi'ch tai Thuc hien nam Idn cdc thao tde va d tren, umg vdi cung vi tri (1) da chgn cua \ at 16 5, Xac dinh tieu c u / c u a tiiau iviiih phan ki L theo cdng thiic (35.1), vdi chu y quy irdc ve ddu dai sd cua cdc dai lugfng d, d' va/ 221 BAO CAO THI NGHIEM Hg va ten : Td Ldp 1.Ten bai thiic hanh Bang thUc hanh 35.1 Vitrl(1)cua vat/A6 : (mm) t Lan d (mm) Af(mm) f(mm) \d'\ (mm) i i Trung binh 7- (mm) Af= _ Tmh ket qua cua phep Bang thifc hanh 35.1 - Tinh gid tri tieu cir/ciia thau kfnh phan ki L mdi Idn - Tfnh gia tri trung binh J ciia cdc Idn - Tinh sai sd tuyet ddi ctia mdi Ian - Tinh sai sd tuyet ddi trung binh A/ cua cdc Idn Tfnh sai so ti ddi trung binh - 171 Viet ket qua cua phep / = / ± A/ = vdi 5= 222 + (mm) (mm) CAU HOI Viet cong thiic thau kinh va noi ro quy uoc ve dau ciia cac dai lupng co cong thiic Hay noi ro cdch xac dinh diing vi tri anh ro net ciia mot vat hien tren man anh dat d phia sau Trinh bay phuong phap tieu cu cua thau kinh ^lia met thau kinh hoae cua mot he thau kinh.^ phan ki L da dupc thuc hien thi nghiem Hay cho biet nhung nguyen nhan nao co the gay nen sai sd ngau nhien ciia phep tieu cu Ve anh that cua mot vat that AB dat vuong goc ^^^au kinh phdn kl L thi nghiem ndy vdi true chinh ciia mot he hai thau kinh dong true L, LQ Cho biet thau kinh phan kl L dat gan Co the thuc hien phep tieu cu f ciia thau kinh phan ki L bang each ghep no dong true vat AB hon so vdi thau kinh hoi tu LQ va anh vol mot thau kinh hoi tu LQ, nhung vat that cuoi ciing tao bdi he thau kinh la anh that dupc ddt gan thau kinh hoi tu hon so voi thau kinh phdn ki dugc khong ? Co the xac dinh tieu cu ciia thau kinh hoi tu Lg tien hanh thi nghiem ndy dugc khong ? Neu biet, em hay noi rd noi dung thuoc phan nao ciia bai thi nghiem Neu biet, em hay trinh bay ro cdc budc tien hanh thi nghiem va ve hinh minh hoa sy tao anh ciia vat 223 T ong ket lyi^T chuong VI! C A C DUNG CU QUANG Bd phan va dung cu Cdu tao Dac diem Cdc ket qua vd cdng thiic (1) (2) (3) (4) Lang kinh Khdi chat sud't hinh lang tru tam gidc - Tde dung : -h Tan sdc -t- Ldm lech tia 16 ve ddy - Khdi chat - Thdu kinh hdi tu : sudt gidi han bdi : -h/>() + Hai mat cdu Thau kinh -t- Hoae mdt mat cdu vd mgt mat phdng - Hai loai : Hgi tti vd phan ki + Anh > vat j - Nhin thdy mot vdt: - The thuy tinh Anh that hien a mang luoi - Dieu net : Thay doi tieu cu : l+Q /nun - Ndng sudt phdn li : £= r 224 -Ddtu : D= ~ f - Cdng thdc : +Vttn:^.- = + So phong dai : + / > „ , or 1.B;2 C ; a ) - c m , / ( = / ; b ) c m ; a) Anh sau cung d vd ci/c ; b) Diing hai tia ^^"9 '^' 9^^ '^'^^'^9 ^^^ ; b) d > 60 cm ; d