Do cdc btfdc song X i va X, b6 hcfn X nen chiing gay hiep ti/cfng quang dien doi vdri t a r n k i m loai Vay chgn dap an C Cdu 25: Trong mach dao dong LC h tirdng dang c6 dao dong dien ti^ tii do, dien tich cua mot ban tu dien va ctfdng dong dien qua cuon cam bien thien dieu ho a theo thdi gian D luon ngiiac pha C luon cung pha B vdi cung tan so A vdi cung bien Trong mach dao dong LC l i tifdng dang c6 dao dong dien tCf tif do, dien tich cua mot ban tu dien va ciJcfng dong dien qua cuon cam bien thien dieu hoa theo thcfi gian vdri cung tan so Vay chon dap an B Cdu 26: Nguyen tijT hidro dang or trang thai cor ban c6 bang -13,6eV De chuyen ien trang thai difng c6 mufc mufc nang liTOng nSng lircfng -3,4eV thi nguyen tuf hidro phai hap thu mot photon c6 nang lifc^ng: A 17 eV B 10,2 eV C eV D - , eV Giai Nguyen tuT hidro phai hap thu mot photon c6 nang lutfng: s = hf = E - E , = - , - ( - , ) = 10,2eV Vay chon dap an B Cdu 27: Dat dien ap xoay chieu vao hai dau doan mach c6 R, L, C mkc noi tiep Biet R = 10 Q , cuon cam thuan c6 L = 10'^ IOTI va dien ap giufa hai dau cuon cam thuan la Bieu thufc (H), tu dien c6 C = 2n (F) = 20>/2 c o s 1007rt + - (V) dien ap giufa hai dau doan mach la: A u = 40 cos 1007rt + r j (V) C u = 40V2cos 1007rt + - \ l O O T r t - - (V) B u = 40V2cos 4j D u = 40cos ^ G O T c t - - ' (V) (V) Giai Tac6: Z, =coL = 10071 IOTI = 10Q 38 Gi4i Chi ti«it (JS thi T S B H , C D M6n V$t l(