mat NgLfcfi c a n t h i 50 xa v6 c m , deo C L T C m a c6 diem k i n h c6 mat C L T C Giai can each mat tu -2 10 diop sat m a t c m , d i e m ciic v i l n t h i c6 the n h i n ro each vat of k h o n g c a n dieu tiet Vay chqn dap an D Cdu 48: V a t sang A B c6 dang m o t doan thSng, dat vuong goc vdi true chinh ( A n k m t r e n true chinh) cua mot thau k i n h , tao anh A i B i = 4em ro n e t t r e n m a n Giuf v a t va m a n co d i n h , d i chuyen t h a u k i n h doc theo true c h i n h den m o t v i t r i khac t h i l a i t h u diTOc a n h A2B2 = 6,25cm r5 net t r e n m a n Do cao v a t A B bkng: A 1,56 cm B 25 cm C cm D 5,12 cm Giai T a c6 v i t r i : _ d A'B' - V i t n l : — = = d' AB AB _ V i t r i : l =^ d' A"B" (1) =^ (2) 6,25 G i a i he gom h a i phifcfng t r i n h (1) va (2) ta duac A B = Vay chon dap an C Cdu 49: M o t tha'u k i n h m o n g bang t h u y t i n h h a i m a t cau l o i , c6 chiet suat tuyet doi n T h a u k i n h c6 t u : A a m k h i d a t t r o n g m o i triicfng c6 chiet suat tuyet doi n ' < n B difcfng k h i dat t r o n g m o i trUofng c6 chiet suat tuyet doi n ' = n C a m k h i dat t r o n g m o i tri/ofng c6 chiet sua't tuyet doi n ' > n D luon dUtfng, k h o n g phu thuoc vao m o i tn/cfng chufa thau k i n h G\k\ M o t t h a u k i n h m o n g hkng t h u y t i n h h a i m a t cau l o i , c6 chiet suat tuyet doi n T h a u k i n h c6 t u a m k l i i dat t r o n g m o i trUcfng c6 chiet suat tuyet doi n ' > n Vay chgn dap an C Cdu 50: M o t k i n h t h i e n v a n quang hoc gom v a t k i n h va t h i k i n h l a cAc t h a u k i n h h p i t u c6 t i e u CLT I a n li/crt la 1,2 m va cm M o t ngifcfi m^t k h o n g C O t a t , quan sdt m p t t h i e n the of r a t xa hkng k i n h t h i e n v a n t r o n g t r a n g t h a i m ^ t k h o n g dieu t i e t c6 goc t r o n g a n h la 5' Goc t h i e n the k h i k h o n g d u n g k i n h l a : A 0,5" B 0,25' C 0,35', 22 • D 0,2' GAi Chi ti^t 66 thi TS BH, C B M6n V^t l(