Giáo trình vật lý đại cương phần 2 (dành cho sinh viên đh chính quy ngành y dược)

P h a n thCr b a m e n T if 95 Chuong TlNH DIEN ■ Khai niem m d dau 1.1 Sir nhi£m dien co sat Tir the ky VI trudc cong nguyen, ngudi ta da nhan thay dem co sat thuy tinh, ebonit va mot so vat khac vao len da, thi thuy tinh, ebonit co kha nang hut cac vat nhe nhu giay vun, long chim Hien tupng goi la hien tupng nhiSm dien co sat Thuy tinh, ebonit dupe goi la vat nhiim dien Qua su nhiim dien co sat, nguai ta thay chi xuat hien loai dien tfch: - Loai dien tfch xuat hien giong nhu a thuy tinh co sat vao len da goi la dien tfch duang (+)• - Loai dien tfch xuat hien nhu d ebonit co sat vao len da goi la dien tfch am (-) Qua thuc nghiem thay cac loai dien tfch tuang tac vai nhau: hai dien tfch cung dau thi day nhau, khac dau thi hut 1.2 Sa lirac ve thuyet dien tir Qua nhieu thi nghiem cac nha bac hoc da di den ket luan: - Dien tfch tren mot vat mang dien bat ky co cau tao gian doan, no luon luon bang mot sd nguyen lan cua mot dien lupng nhd nhat goi la dien tfch nguyen to: dien tfch nguyen to cd gia tri |q0| = 1,6.10'19C Cac hat mang dien tfch nguyen to cd electron mang dien tfch nguyen to am, proton mang dien tfch nguyen to duang - Proton va dien tir (electron) deu cd phan cau tao nguyen tir cua moi chat Proton nam d hat nhan nguyen tir, dien tir chuyen dong xung quanh hat nhan - trang thai binh thudng so proton va dien tir cua mot nguyen tir luon luon bang (bang sd thu tu Z cua nguyen to bang tuan hoan Mendeleep), ta ndi nguyen tir trung hoa ve dien Neu vi ly nao dd nguyen tir mat thu them dien tir se trd mot phan tir mang dien Neu mat dien tir nguyen tir se mang 97 dien duong goi la ion (+), neu thu them dien tir nguyen tir trd mang dien am goi la ion (-)• Hoe thuyet can cu: vao chuyen dong cua dien tir de giai thfch cac hien tuong ve dien goi la thuyet dien tir 1.3 Dinh luat bao toan dien tich Cac hien tupng v6 dien luon luon tuan theo dinh luat bao toan dien tfch: Cac dien tich khdng the tit nhien sinh ra, cung khong tit bien ma't, no chi cd the truyen tit vat sang vat khac hoac phan sang phan khac ciia vat Noi mot cach khac: Tong dai so cac dien tich mot he cd lap Id khdng doi Thf du: Khi co sat thuy tinh vao len da, neu thuy tinh mang dien duong thi dien tir tir thuy tinh da mat di, co nghla la no phai chuyen sang len da, do len da phai mang dien am Do ldn dien tfch tren hai vat luon luon bang neu trudc dd hai vat d£u chua mang dien 1.4 Vat d in dien, vat cach dien 1.4.1 Vat ddn dien La nhung vat ma dien tfch cd the chuyen dong tu toan bo the tfch cua vat Thf du nhu kim loai, cac dung dich dien phan, chat khf da bi ion hoa, cac co the song 1.4.2 Vat cach dien (dien mdi) La cac vat ma dien tfch khdng thi chuyen dong tir diem den didm cua vat (khdng cd dien tfch tu do) Thf du: Thuy tinh, ebonit, cao su, gd, khdng khf kho C hi y: Su phan chia vat din dien va each dien chi cd tfnh chat quy udc Thuc vay nhung dieu kien nhat dinh vat nao cung cd the dan dien dupe, chung chi khac la dan dien nhieu hay ft Khi thay ddi dieu kien thi tfnh dan dien thay doi Thf du: thuy tinh d dieu kien binh thudng dan dien rat yeu (khong dan dien) nhung d nhiet cao cd the dan dien Ngoai ra, cd mot nhom chat cd tfnh chat dien va dien mdi Dd la cac chat ban dan dan dien trung gian giua vat dan Trong chuong chi nghien cuu tuong tac va tfnh chat ciia cac dien tfch dung yen (so vdi he quy chieu dung de nghien cuu dien tfch dd) 98 Djnh lu at Culdng (Coulomb) Nhir ta da biet cac dien tfch tuang tac vai nhau: cung dau thi day nhau, khac dau thi hut Tuang tac giua hai dien tfch durng yen goi la tuong tac tinh dien (hay la tuong tac Culong) Nam 1875, Culong nha bac hoc nguai Phap bang thuc nghiem da xac djnh duoc luc tuong tac giua hai dien tfch diem 2.1 Dien tich diem La nhung vat mang dien co kfch thuoc nho khong dang ke so v6i khoang cach tur diem den nhung diem hoac nhung vat mang dien khac ma ta dang khao sat Nhu vay, khai niem dien tfch diem chi co tfnh chat tuong doi, tuong tu nhu khai niem chat diem co hoc 2.2 Djnh luat Culong chan khong Gia sir co hai dien tfch diem q,, q2 dat chan khong cach mot khoang r Dinh luat Culong phat bieu nhu sau: Luc tuang tac giua hai dien tich diem co phuong nam tren dudng thdng noi hai dien tich, co chieu: dien tich cung dau thi day nhau, dien tich khac dau hut (hinh 1.1) Co Ion ty le thuan voi tich so Ion cua hai dien tich, F2 +q, f„ ty le nghich voi binh phuong khoang cach < = -• ► giua hai dien tich Ve mat lan, ta co: F2, = F12 = k.k lW + •- r Hinh 1.1 k la he so ty le Trong he SI: k = —— ; s0duoc goi la hang so dien, co gia tri: tie e0—8,86.10 (N C m ) k = 9.109 (N C2m2) Ta co the bieu diin dinh luat Culong dudi dang vecto nhu sau: Ke vecto r goc q, ngon q2 thi: F = 12 47ie0 r2 r ^ = -F |2 m ^ (2 ) 99 2.3 Dinh luat Culong cac moi trudng Thuc nghiem cung chting to neu hai dien tich diem dat chat dien moi co cung khoang cach nhu chting dat chan khong thi luc tuong tac se giam di e lan Cong thtic (1) se la: F = ! M i l (3) 12 47t£0.£ r2 r do, £ dupe goi la hang so dien moi phu thuoc vao ban chat cua dien moi, nhiet Thi du: Trong chan khong £ = Khong khf: e = 1,006 «1 Nude £ = 81 Chu y: Dinh luat Culong mdi chi cho ta xet tuong tac giua hai dien tich diem Tuy nhien neu ap dung nguyen ly tong hop luc co hoc, ta cd the xet tuong tac giua hai vat mang dien bat ky That vay: - Neu he gdm nhieu dien tfch diem q b q2, qn phan bo gian doan khdng gian va mot dien tfch q0 dat khdng gian dd Ta xet tuong tac tting he dien tfch q, va q(); q2 va q„, , qn va q(), ta se cd: F = F'l0+F'20+F30+ +FnO P -± * 1=1 - Neu vat mang dien bat ky Ta cd the chia vat vd so phan mang dien rat nhd hop thanh, mdi phan nhu the coi nhu dien tfch diem - Dua vao phuong phap tfnh toan tren day ngudi ta chting minh dupe tuong tac giua hai qua cau mang dien deu cd cd the xac djnh bang dinh luat Culong song phai coi dien tfch cua mdi qua cau nhu mot dien tfch diem nam d tam qua cau Dien trtfdng cua cac dien tfch diem 3.1 Khai niem ve dien trudng Ta da biet cac dien tfch tuong tac vdi ca chung dat chan khdng CJ day cd the dat nhieu cau hoi: Luc tuong tac dd truyen di nhu the nao? Co can mdi trudng xung quanh khdng? Khi chi cd mot dien tfch thi mdi trudng xung quanh cd gi thay doi? 100 D e tra lai cac cau hoi tren qua trinh phat trien cua vat ly hoc da co hai gia thuyet doi lap nhau: Thuyet tac dung xa, thuyet tac dung gan T heo thuyet tac dung xa, dien tfch tuang tac vai khong can m ot m oi trudng trung gian ma no duoc truyen tijr dien tfch den dien tfch m ot cach tuc thai vai van toe vo cung lan Cung theo thuyet neu chi co m ot dien tfch thi m oi truang xung quanh dien tfch khong bien doi gi Thua nhan thuyet tuang tac (tuc la truyen van dong) khong can thong qua vat chat, thuyet tac dung xa da thua nhan co van dong phi vat chat do thuyet da bi bac bo Trai vai thuyet tac dung xa, thuyet tac dung gan cho rang xung quanh m 6i dien tfch co xuat hien m ot dang vat chat “dac biet” goi la dien truang N hd dien truang, cac dien tfch m oi tuong tac duac vai nhau, van toe truyen phai la huu han Mot tfnh chat c o ban cua dien trudng la dat m ot dien tfch dien truang thi deu bi dien truang tac dung luc Khoa hoc hien dai da chung minh thuyet tac dung gan la dung V ay xung quanh dien tfch dung yen xuat hien m ot dien truang D ien truang la mot dang cua vat chat 3.2 Vecta cudng dien truang 3.2.1 Dinh nghia Gia su' co m ot dien tfch q0 dat tai m ot diem dien trudng D ien tfch qn rat nho de no khong lam thay doi dien truang m a ta dang xet, dien tfch q„ duac goi la dien tfch thu (q()> 0) Thuc nghiem chung to: F E = — = const q0 (4) doi vai m ot d ilm xac dinh E duac goi la vecto' cudng dien trudng Vay: Vecta cudng dien trudng tai mot diem Id mot dai luong vecto co gia tri bang luc cua dien trudng tac dung len mot dan vi dien tich duong dat tai V i vay v e cto cudng dien trudng dac trung cho dien trudng ve phuang dien tac dung luc Trong he SI dan vi cua E la (V m ') 3.2.2 Vecto cudng dien trudng gay boi mot dien tich diem Gia su co m ot dien tfch diem q X ung quanh q co m ot dien trudng Tai mot diem M cach q m ot khoang r neu ta dat dien tfch q() T heo dinh luat C ulong, lire tac dung cua dien trudng q len q0 la: 101 F— q gp r 47re0.e r2 r E= — = — -— q0 4.7t.s0.8 r r Dodo: (5) Ro rang: q >0 thi E cung chieu r q q0 q < thi E nguoc chieu r q _ ^ Ve Ion: E = — -— ^y 47i.e0.e r Hinh 1.2^ 3.2.3 Vecta cudng dien trudng he dien tich diem Gia su co he dien tich diem q,, q2, qn Tai mot diem M dien trudng he dien tfch diem tren gay neu ta dat dien tfch thu q0 Ta co: „ Fq(, =FQiq.i +F F= Fq° = F qo q0 + +Fq,,q„ F q» _|_ _|_Fqnq.i q« Qo = E,+E2+ +En E=lE , /=l (6) Bieu thuc (6) duoc goi la nguyen ly chdng chat cua dien trudng 3.3 Luong cuc dien 3.3.1 Dinh nghia Ludng cuc dien la he hai dien tich diem cd dien tich bang vd trai da'u (+q, -q) cach mot khoang I rat nho so vdi khoang cach tif ludng cuc dien tdi diem dang xet De dac trung cho ludng cuc dien, ngudi ta dung mot dai luong vat ly goi la momen ludng cuc dien, duoc dinh nghla: q do, q la ldn cua mdi dien tfch J duoc ke tir - q den +q 102 q-q Hi nh M C.33.44.55.54.78.65.5.43.22.2.4 22.Tai lieu Luan 66.55.77.99 van Luan an.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.33.44.55.54.78.655.43.22.2.4.55.22 Do an.Tai lieu Luan van Luan an Do an.Tai lieu Luan van Luan an Do an Dudng thang noi giua q va -q duoc goi la true luong cuc dien 3.3.2 Dien trudng ludng cuc dien gay De don gian ta chi xet cuong dien truong luong cuc dien gay tai nhung diem nam tren duong trung true cua /, each / mot khoang r » / Theo nguyen ly ch6ng chat cua dien truong ta co: E = E, +E Ve ldn: E+ = E = 47te0e r; r =r + Vi r » / nen r2 « r2 Vay E+ = E = —^— A 47I£0£ r" E co phuong song song vdi / , co chieu nguoc chieu vdi / c-T c ,cosa=2.E^.— c I = -1 =q./ Pe E =E=2.E, 2r 47ie0£ r 47i£0£ r Tom lai ta cd: E=— 47t£0£.r (7) 3.3.3 Ludng cuc dien dien trudng Gia su cd mot ludng cuc dien dat dien trudng deu, vecto cudng dien trudng E lam vdi Pc mot goc a Cac dien +q tich +q va -q se chiu mot luc tac dung cua dien trudng: F = qE Hinh 1.5 F = -q E F va F lam mot ngau luc co momen ngiu luc la: M = P a E (8 ) Dudi tac dung cua M ludng cuc dien se bi quay cho Pe trung vdi phuong cua E va tai dd M = 0, ludng cuc dien d trang thai can bang 103 Stt.010.Mssv.BKD002ac.email.ninhd 77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77t@edu.gmail.com.vn.bkc19134.hmu.edu.vn.Stt.010.Mssv.BKD002ac.email.ninhddtt@edu.gmail.com.vn.bkc19134.hmu.edu.vn C.33.44.55.54.78.65.5.43.22.2.4 22.Tai lieu Luan 66.55.77.99 van Luan an.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.33.44.55.54.78.655.43.22.2.4.55.22 Do an.Tai lieu Luan van Luan an Do an.Tai lieu Luan van Luan an Do an * Chu y: - Trang thai can bang cua ludng cuc dien phu thuoc vao chuyen dong nhiet cua cac phan tir luong cuc - Neu luong cuc khong vung chac thi qua trinh quay, no co thi bi bien dang * ling dung thuc te: Nau nudng bang lo vi song Mot phan tu nuoc (H20 ) la mot luong cuc dien Oxy va nguyen tu hydro lien ket vdi khong nam tren cung mot duong thang ma tao mot goc chung 105° (hinh 1.6) Ket qua la phan tu nude cd hai phfa xac dinh, phfa oxy va phfa hydro Ngoai 10 dien tu phan tu nude cd xu hudng d gan hat nhan oxy hon gan hat nhan hydro Dieu lam cho phan tu nude tao mot ludng cue dien, phfa duong la hydro, phfa am la oxy Hinh 1.6 Trong*nudc, cac phan tu cd the chuyen dong tuong ddi, dien trudng mdi ludng cue dien sinh anh hudng den cac ludng cue dien xung quanh Ket qua la cac phan tir nude cd the lien ket nhom hoac nhom phan tu (hinh 1.6) (vi dau am cua phan tu ludng cue hut dau duong cua phan tu ludng cue khac) Mdi lan hinh mot nhom nhu vay, the nang dien dupe chuyen dong nang chuyen dong cua cac phan tu' Va mdi lan va cham mot nhom tan thi nang lupng lai chuyen theo chieu nguoc lai Nhiet ciia nude khdng thay doi vi trung binh su chuyen doi nang lupng tong cong bang khdng Khi lo vi song hoat dong, cac song micromet tao lo dien trudng xoay chieu (vdi cac lo vi song bien hien tan so f = 10l4Hz) Neu lo cd H20 , cac phan tu ludng cue nude quay tdi, quay lui mot each lien tuc de dinh hudng md men ludng cue dien theo dien trudng Cac phan tu ludng cuc lien ket cap cd the quay quanh mdi lien ket chung, chung cd thi dinh hudng theo dien trudng Tuy nhien, cac lien ket nhom ft nhat mot phan tir bi gay nhom lien ket va luc dd giai phdng nang lupng dudi dang nhiet, nude nong len Vay lo vi song nang lupng song dien tir da chuyln nhiet nang 104 Stt.010.Mssv.BKD002ac.email.ninhd 77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77t@edu.gmail.com.vn.bkc19134.hmu.edu.vn.Stt.010.Mssv.BKD002ac.email.ninhddtt@edu.gmail.com.vn.bkc19134.hmu.edu.vn C.33.44.55.54.78.65.5.43.22.2.4 22.Tai lieu Luan 66.55.77.99 van Luan an.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.33.44.55.54.78.655.43.22.2.4.55.22 Do an.Tai lieu Luan van Luan an Do an.Tai lieu Luan van Luan an Do an dung Khoai tay m^m la qua trinh t6 ng hop acid nhan nhung diem sinh trucmg Viec chieu xa co the lam cham qua trinh t6 ng hop lai Doi v6 i triing gay hai, ngoai viec tieu diet ban than trung bang tia xa, nguoi ta muon tao nhung thuoc tinh di truyen bat lpi gay vo sinh cho trung due roi tung chung vao moi trucmg chung sinh song Ky thuat co nhieu lpi ich vi voi lieu khoang 8000R co the la due mat kha nang sinh san, tao nhung trting ung va sau mot thoi gian, ca tap hop trung bi diet vong Tir trudc toi thuftng khir trung dung cu y te, chi kMu, thuoc, vaccin bang hoa chat (thuoc sat trung, tffy rua, ) va nhiet nang (luoc, hap, say, dot, ) Cac cach xir ly khong phai luc nao cung ap dung dupe va co the lam hu hong mot ph^n hoac toan bo san ph^m Tu sau dai chien the gidi thu hai, nguoi ta ap dung rong rai viec dung btic xa ion hoa de tieu diet cac vi sinh vat cac san pham y te da neu tren Ngay nhieu loai thuoc, gang phau thuat, dung cu tiem truyen, dung cu phau thuat dupe xuat xuong sau ap dung viec khu trung bang btic xa ion hoa Thuc viec xac dinh cai chet cua vi sinh vat day rat kho Thong thucmg chi co the kiem tra su “vo trung” cua san pham ma thoi Lay nhung m iu vat cua san ph^m^ u nhiet thuan lpi cho su phat trien cho su phat trien cua vi khucin (30°C, 37°C va 55°C), nuoi cay tiep vao nhung moi trucmg thich hop, neu khong tha'y vi khuan phat trien (moc cac khudn lac hoac lam thay doi moi truefng nuoi cay vi khu^n) thi dupe coi la “vo trung” - Tieu huy hoac kim ham su phat trien cua cac te bao benh nhu te bao ung thu, te bao noi tiet cu5ng nang, phat trien qua manh Du6 i tac dung cua btic xa ion hoa, cac te bao benh bi kim ham sinh san hoac bi pha huy, ltic cac te bao lanh xung quanh it bi hu hai la do nhay cam phong xa cua chung khac va bang cac kl thuat chuyen mon, nguoi ta lam cho lieu hap thu vao cac mo benh nhieu hon mo lanh Co nhieu cach chieu xa dieu tri Do la cac kl thuat dung nguon chieu dat tir ngoai co th£ (teletherapy) hoac dung cac nguon gamma yeu, beta cting ap sat mo benh (brachytherapy) hoac dua cac nguon phong xa ho vao tan mo benh (curietherapy) - Kich thich cay trong, hat giong va gay dot bien gen co lpi de tao giong moi Ket qua nghien ctiu cho thay vcti mot lieu nhat dinh co the tang thu hoach va thuc d^y su phat trien cua cay Co the dieu khien su sinh truong va phat trien cua cay bang cach lira chon chieu xa vao nhung thdi ky phat trien nhat dinh cua cay So di vay la vi btic xa da tac dong len su phan chia te bao cay Chieu nhurng lieu nho vao hat giong tru c gieo co the kich thich sinh truong nhanh, chong gay benh va rut ngSn thoi gian thu hoach 212 Stt.010.Mssv.BKD002ac.email.ninhd 77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77t@edu.gmail.com.vn.bkc19134.hmu.edu.vn.Stt.010.Mssv.BKD002ac.email.ninhddtt@edu.gmail.com.vn.bkc19134.hmu.edu.vn C.33.44.55.54.78.65.5.43.22.2.4 22.Tai lieu Luan 66.55.77.99 van Luan an.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.33.44.55.54.78.655.43.22.2.4.55.22 Do an.Tai lieu Luan van Luan an Do an.Tai lieu Luan van Luan an Do an Cac ngu6 n phong xa bang “ Co va 137Cs thudng dupe dung vao muc dich Btic xa ion hoa co th£ gay n£n nhung bien d6 i d cac chat lieu di truyen la ADN va RNA, tao cac dot bien Co che gay dot bien ra't phtic tap va thuoc vao btic xa, sua't lieu, lieu lupng Ngudi ta da tien hanh dong loat thi nghiem, chon lay nhung ca the co xuat hien nhung dot bi6'n co lpi, cung co no va nhan len qua nhieu the h6 Tti co th£ tao mot giong mdi n dinh nhung thuoc tfnh mdi Do la nhung cong viec cong phu, keo dai hang chuc nam Bang 5.1 cho ta mot vai vf du da thu dupe Bang 5.1 NhOmg dot bien thu difoc bang chieu xa d mot so cay Chung dot bien Cay Dia diem va thdi gian tao dot bien Uii diem mdi xuat hien Cai dau he Regina Thuy Dien, 1953 Nang suat cao Lua mach miia dong Jutta Dtic, 1953 Chiu ret, nang sua't cao Yen mach Florad Florida, 1960 Khang benh tan lui Lua mach mua xuSn Mari Thuy Dien, 1960 Chin sdrm Lua mi NP 836 An Do, 1960 Dai cuong, chiu han, nang suat cao An toan phong xa Chung ta da tha'y ro tac dung to ldn cua btic xa ion hoa len cac t chtic sinh hoc Vi vay, de ngan ngtia hoac han che dupe tac hai cua cac tia phong xa len co the’ ngudi va tranh lam o nhi6 m moi trudng song, chung ta phai thuc hi6 n nhung cong viec d£ dam bao an toan su dung va tiep xuc vdi cac ngu n phong xa 5.1 NhOmg nguon chieu xa anh hudng den ngudi Co the ngudi co the bi chieu xa tti ben ngoai Do la cac tia co kha nang dam xuyen Ion nhu tia X, tia gamma, chum hat notron, chum tia beta cting Cac dong vi phong xa cung co th£ bang nhieu cach khac lot vao ben co th£ tao nguon chieu xa tti ben co the Cac nguon xa xuat phat tti cac nguon phong xa tu nhien va nguon xa nhan tao (Bang 5.2) Nguon phong xa tu nhien bao gom cac tia vu tru, cac btic xa ion hoa phat tti cac dong vi phong xa da co san tu nhien nhu 40K, 3H, 14C va tti cac dong vi cua dong ho phong xa tu nhien la dong uran - radi, dong thori va dong actini Nguci ta da tfnh toan dupe rang tti cac nguon phong xa tu nhien lieu chieu tren 213 Stt.010.Mssv.BKD002ac.email.ninhd 77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77t@edu.gmail.com.vn.bkc19134.hmu.edu.vn.Stt.010.Mssv.BKD002ac.email.ninhddtt@edu.gmail.com.vn.bkc19134.hmu.edu.vn C.33.44.55.54.78.65.5.43.22.2.4 22.Tai lieu Luan 66.55.77.99 van Luan an.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.33.44.55.54.78.655.43.22.2.4.55.22 Do an.Tai lieu Luan van Luan an Do an.Tai lieu Luan van Luan an Do an xucmg ngudi khoang 125 mr/nam 122 mr/nam va li£u chieu tren co quan sinh due la Bang 5.2 Lieu chieu trung blnh dung X quang chup y te Ca quan, phu tang chup Dien the bong X quang (kV) Lieu chieu (bang r) Ban va ngon tay 40-50 0,06 Canh tay 55-65 0,7-1 So nao nghieng 60-65 ,8 - 1,2 So nao thang 65-75 ,2 - 1,6 Cot song nghieng 70-85 1,8 - 3,5 Cot song thang 65-75 1,6 - 2,5 Khung chau 70-75 2-2 ,5 Phoi 60-75 0,04 - 0,2 Da day 75-90 1,5-3 Than 65-85 1,4-2,5 Rang 50-60 -5 Tim 85-90 -4 Chup thai -8 Nguon phat xa nh&n tao la cac btic xa ion hoa phat tir cac ngu n phat tia X dung y te va cong nghiep, tti su o nhilm moi trufrng nguoi sir dung cac nguon phong xa ho nhu 131I, 32P hoac tit cac can ba cua cac vu no hat nhan thi nghiem nhu 137Cs, 90Sr, 89Sr Lieu luong gay nguon phong xa nhan tao r£t khac nhau, thuoc timg noi, tting ngudi vdi cac nganh nghe va cong viec khac 5.2 Lieu toi da cho phep Mod d&u, sir dung cac tia phong xa, ngufti ta chua co du hieu biet de giu gin an toan phong xa Do da xay cac tai bien chet nguoi, cac benh nghe nghiep btic xa Tuy nhien, khong the tao duoc mot moi trucmg tuyet doi khong co cac btic xa ion hoa chieu vao co the nguoi thuc te Va lai nguoi ta da da hieu dupe r&ng ngucfi tir phat sinh va ton tai den luon luon v^n phai chiu tac dung cua mot lieu chieu phong xa nhat dinh moi luc, moi noi Tuy v^y, loai ngudi vSn ton tai va phat trien ca the luc va tri tue, ca so luong va hlnh thai Vi vely, ngudi ta tin chdc rSng ton tai mot lieu nguong ma 214 Stt.010.Mssv.BKD002ac.email.ninhd 77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77t@edu.gmail.com.vn.bkc19134.hmu.edu.vn.Stt.010.Mssv.BKD002ac.email.ninhddtt@edu.gmail.com.vn.bkc19134.hmu.edu.vn C.33.44.55.54.78.65.5.43.22.2.4 22.Tai lieu Luan 66.55.77.99 van Luan an.77.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.37.99.44.45.67.22.55.77.C.33.44.55.54.78.655.43.22.2.4.55.22 Do an.Tai lieu Luan van Luan an Do an.Tai lieu Luan van Luan an Do an khdng phat hien tha'y tac hai cua no Do la lieu toi da cho phep tire la lieu toi da co th£ chap nhan dupe Viec xac dinh gia tri cua lieu ngudng xay rat dai bdi vi trudc nam 1928 ngudi ta chua co khai niem ro ret ve tac hai cua buc xa Nam 1950, Uy ban Quoc te ve An toan Phong xa ICRP (International Committee of Radiation Protection) xac dinh lieu toi da cho phep la 0,2 r/ngay roi ve sau giam xuong 0,1 r/ngay Nhd cac nghien curu thuc nghiem nen tCr nam 1954 xac dinh lai lieu la 0,3r/tuan Nam 1956 tren co sd ve nhung lo lang ve tac dung di truyen,ngudi ta quy dinh mure tha'p han la 0,1 rem/tuan tuc la rem/nam Ngay ngudi ta khdng quan niem curng nhac nhu vay nua ma xuat phat tu nguyen tac la co gang giam lieu xuong cang thap cang tot, thira nhan rang mot lan chieu den 25 rem la khdng co tac hai gi dang lo ngai 5.3 Cac bien phap chu yeu de dam bao an toan phong xa Tac dung sinh hoc cua burc xa ion hoa trudc het phu thuoc vao ban cha't va nang luong tia, lieu luang, suat lieu va nhieu yeu to khac Cac nguon phong xa hd lai co the gay nen su nhidm xa vao ben ca th£ va o nhi6 m mdi trudng Vi vay d£7 dam bao an toan phong xa can co cac bien phap ve ky thuat va to chtic lam viec Muon giam duac lieu dieu kien va trudng hap cu th£ co the thuc hien dong thdi nhieu hoac mot nhung bien phap sau day: 5.3.1 Dieu chinh hoat nguon phong xa Mot nguon phong xa co tdc phan ldn se tao nen lieu chieu ldn Vi vay, can phai sir dung nhung nguon toi thieu can cho nhu cau cong viec Nguon toi thieu a day la nguon co tdc phan phong xa du d£ dat duac muc dich cong viec ma khdng qua ldn Trong y hoc, ngudi ta sir dung nhung nguon co tdc phan hang nghin Ci cua Cs137, Co60 de dieu tri ung thu hoac chi vai (j Ci cac nghien euu te bao va phan tu Cudng va nang luang cua nguon quang tuyen X va cac may gia tdc duac dieu chinh qua cudng dien tir trudng va mat hat duac gia tdc 5.3.2 Dieu chinh trudng chieu, tang khoang cach va giam thdi gian tiep xuc Vdi mot chum tia nhat dinh lieu luang hap thu thuoc vao trudng chieu Neu chieu 500r len toan ca the co the xay tir vong Nhung vdi each phan lieu nho va chieu khu tru lieu dieu tri co the dat den hang ngan r ma t