$$P = P_1 + P_2 = \frac{100}{20} + \frac{100}{-10} = 5 - 10 = \boxed{-5 \text{ D}}$$
Back to NEET UG 2026 Optics
NEET UG 2026 — Physics Optics
easy
mcq
2026
Official previous-year question
Verified 30 May 2026.
Question
Two thin lenses of focal lengths $f_1 = +20 \text{ cm}$ and $f_2 = -10 \text{ cm}$ are in contact. The power of the combination is:
Options
- A
$-5 \text{ D}$
- B
$+5 \text{ D}$
- C
$-3 \text{ D}$
- D
$+3 \text{ D}$
Solution
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