Question

What is the position and nature of image formed by lens combination shown in figure? $(f_1, f_2$ are focal lengths)

• A. $70 \,cm$ from point $B$ at left; virtual
• B. $40\, cm$ from point $B$ at right; real
• C. $20/3 \,cm$ from point $B$ at right , real
• D. $70\,cm$ from point $B$ at right, real

Answer 1

Answer: (D)

$70\,cm$ from point $B$ at right, real

Answer 2

For first lens
$\frac{1}{V} - \frac{1}{-20} = \frac{1}{5}$
$V= \frac{20}{3}$
For second lens
$V= \frac{20}{3} - 2 = \frac{14}{3}$
$\frac{1}{V} - \frac{1}{\frac{14}{3}} = \frac{1}{-5}$
$V = 70 cm$