JEE MAIN - Physics (2019 - 12th January Morning Slot - No. 5)
What is the position and nature of image formed by lens combination shown in figure ? (f1, f2 are focal lengths)
_12th_January_Morning_Slot_en_5_1.png)
$${{20} \over 3}$$ cm from point B at right, real
70 cm from point B at right ; real
40 cm from point B at right; real
70 cm from point B at left ; virtual
Explanation
For first lens
$${1 \over V} - {1 \over { - 20}} = {1 \over 5}$$
V $$=$$ $${{20} \over 3}$$
For second lens
V = $${{20} \over 3}$$ $$-$$ 2 $$=$$ $${{14} \over 3}$$
$${1 \over V} - {1 \over {{{14} \over 3}}} = {1 \over { - 5}}$$
V $$=$$ 70cm
$${1 \over V} - {1 \over { - 20}} = {1 \over 5}$$
V $$=$$ $${{20} \over 3}$$
For second lens
V = $${{20} \over 3}$$ $$-$$ 2 $$=$$ $${{14} \over 3}$$
$${1 \over V} - {1 \over {{{14} \over 3}}} = {1 \over { - 5}}$$
V $$=$$ 70cm
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