Taco: L , = l O l g ^ - = 60 ^ I g ^ - = ^ ^0 I , = lO'l^ K Suy r a : ^ - = 10' V i ci/orng a m t i le nghich vdri b i n h phiTOng k h o a n g each R den nguon am n e n : IL = M = I O ^ C : > ^ = 0 ^ R ^ ^ 0 R , Ij R, R, Goi M l a t r u n g diem cua A B Ta eo: R, = " ^ ^ y ^ ^ 50R, Dodo ^ I3 Taco: = M = ^ L ^ V.y 1,=JV = ^ Rf R' 50- 50- = 400I ° = 101g|^ = l O l g ^ ^ = 101g400 = 26,2 « 26 Vay chgn dap an C Cdu 3: T r o n g t h i n g h i e m Y - a n g ve giao thoa a n h sang, h a i khe dLfore chieu bang d n h sang don sac c6 bifdc song 0,6 |xm K h o a n g each giOfa vhai khe l a m m , k h o a n g each tCf m a t phang chufa h a i khe den m a n quan sat l a 2,5 m , be r o n g m i e n giao thoa la 1,25 cm T o n g so van sdng va van t o i c6 t r o n g m i e n giao thoa l a : A van B 15 van C 17 van D 19 van Giai in, ' — 0,6.10-^2,5 , , , ^ K h o a n g van: = — = -; = 1,5.10 m = 1,5mm a 10 ^ So van s6ng: N , = ^ ^ + = van • 2.1,5 12 So van t o i : N , = — — = van ^1,5 T o n g so van: N = N i + N2 = + = 17 van Vdy chqn dap an C 54 Gi&i Chi tiSt (J6 thi TS B H , CD M n Vat If "