A converging lens of power 6 D is placed in contact with a diverging lens of power −2 D. The power of the combination is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 4 D
For thin lenses in contact the powers add algebraically, \( P=P_1+P_2 \). The power of a converging lens is positive and that of a diverging lens is negative.
\( \begin{aligned} P &= P_1+P_2 \\ &= 6\,\mathrm{D}+(-2\,\mathrm{D}) \\ &= 4\,\mathrm{D} \end{aligned} \)
The positive power means the combination acts as a converging lens.