Question

Consider three converging lenses $L_1,L_2$ and $L_3$ having identical geometrical construction. The refractive indices of $L_1$ and $L_2$ are ${\mu }_1$ and ${\mu }_2$ respectively. The upper half of the lens $L_3$ has refractive index ${\mu }_1$ and the lower half has ${\mu }_2$ as shown in the figure. A point object O has an image at $O_1$ by the lens $L_1$ and at $O_2$ by the lens $L_2$ placed in the same position. If $L_3$ is placed at the same place:

• A. There will be an image at $O_1$
• B. There will be an image at $O_2$
• C. The only image will form somewhere between $O_1$ and $O2$
• D. (a) and (b) are correct

Answer 1

Answer: (D)

Since, due to lens $L_1$, image is formed at $O_1$, hence due to upper part of $L_3$, image will be formed at $O_1$.

And, due to lens $L_2$, image is formed at $O_2$, hence due to lower part of $L_3$, image will be formed at $O_2$.

Hence, image will be formed at both $O_1$ and $O_2$.

Answer-(D).