Two convex lenses have focal lengths of 50 cm and 25 cm, respectively. If these two lenses are placed in contact, then the net power of this combination will be equal to
- A. +2 dioptre
- B. +6 dioptre ✓
- C. -6 dioptre
- D. +3 dioptre
Correct Answer: B. +6 dioptre
Explanation
Power P = \frac{100}{f(\text{in cm})}. P_1 = \frac{100}{50} = +2 \text{ D} and P_2 = \frac{100}{25} = +4 \text{ D}. Net power P = P_1 + P_2 = +2 + 4 = +6 \text{ D}.
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