huynhlyhuynhly30

2 năm trước

Giúp mình với!!!!! Thấu kính phân kì có tiêu cự 24 cm người ta đặt vật sáng AB cao 4 cm vuông góc với trục chính và có a nằm trên trục chính của thấu kính sẽ cho ảnh a phẩy B phẩy cách vật 12 cm a) vẽ ảnh của vật qua thấu kính b) bằng công thức toán học hãy tìm Độ lớn của ảnh và khoảng cách từ vật đến thấu kính

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doanminhphuong342

2 năm trước

Đáp án:

a) Hình vẽ

b) 2cm

Giải thích các bước giải:

a) hình vẽ

b) Ta có:

\(\begin{array}{l}
\dfrac{{AB}}{{A'B'}} = \dfrac{{OA}}{{OA'}} = \dfrac{{OA' + 12}}{{OA'}}\\
\dfrac{{AB}}{{A'B'}} = \dfrac{{OI}}{{A'B'}} = \dfrac{{OF}}{{ - OA' + OF}} = \dfrac{{24}}{{24 - OA'}}\\
\Rightarrow \dfrac{{OA' + 12}}{{OA'}} = \dfrac{{24}}{{24 - OA'}} \Rightarrow OA' = 12cm\\
\Rightarrow A'B' = 2cm
\end{array}\)

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