An object 4 cm tall is placed 15 cm from a convex lens of focal length 10 cm. The image height is
A8 cm (inverted)
B12 cm (erect)
C2 cm (inverted)
D4 cm (erect)
Answer & Solution
Correct answer: A. 8 cm (inverted)
$\frac1v-\frac1u=\frac1f$, $u=-15$: $\frac1v=\frac1{10}-\frac1{15}=\frac{1}{30}\Rightarrow v=30$. $m=v/u=30/(-15)=-2$. Image height $=|m|\times4=8$ cm, inverted.
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