Mỹ Tâmm

2 năm trước

cho trục sáng của AB đặt vuông góc với trục chính của TKPT có tiêu cự bằng 12cm, điểm A nằm trên điểm trục chính và cách thấu kính một khoảng bằng 9cm , AB bằng 1cm .a) hãy dựng ảnh A'B' của AB nêu cách dựng b) nhận xét đặc điểm của ảnh A'B' c) Xác định vị trí của ảnh

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thuisatutor

2 năm trước

Đáp án:

Giải thích các bước giải:

Trương Tiến Nhật

2 năm trước

b, Vì $d<f$

$⇒A'B'$ là ảnh ảo, lớn hơn vật

$ΔABO\simΔA'B'O$

$⇒\dfrac{AB}{A'B'}=\dfrac{AO}{A'O}$

$⇔\dfrac{h}{h'}=\dfrac{d}{d'}$ $(1)$

$ΔIOF'\simΔB'A'F'$

$⇒\dfrac{OI}{A'B'}=\dfrac{OF'}{A'F'}$

$⇔\dfrac{AB}{A'B'}=\dfrac{OF'}{A'O+OF'}$

$⇔\dfrac{h}{h'}=\dfrac{f}{d'+f}$ $(2)$

Từ $(1)$ và $(2)$

$⇒\dfrac{d}{d'}=\dfrac{f}{d'+f}$

$⇔\dfrac{9}{d'}=\dfrac{12}{d'+12}

$⇔d'=36cm$

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