Question

Focal length of convex lens is $100\, cm$ and focal length of concave lens is $8 \,cm$. Find the magnification of the given combination of lens if object is placed at point $O$.

• A. 1.02
• B. 0.04
• C. 2.01
• D. 0.08

Answer 1

Answer: (D)

For first lens
$m_{1}=\frac{v}{u}=\frac{f}{u+f}=\frac{100}{-50+100}=2$
Image distance v = 2u = 2 × (-50) = -100 cm
For second lens
Now u = - 190 cm, f = - 8 cm, m₂ = ?
$m_{2}=\frac{v}{u}=\frac{f}{u+f}=\frac{-8}{-190-8}=0.04$
Net magnification = m₁ m₂ = 0.08