alleryTwo lenses of powers +3 D and -5 D are placed in contact. The combination:
ABehaves like a convex lens of power +2 D
BHas no focal length
CIs opaque
DBehaves like a concave lens of power -2 D
Answer & Solution
Correct answer: D. Behaves like a concave lens of power -2 D
1. For lenses in contact, total power is P = P1 + P2.
2. P = (+3) + (-5) = -2 D.
3. Negative net power means a diverging (concave) lens.
4. So the combination behaves like a concave lens of -2 D.
_Source: Selina Concise Physics ICSE Class 10, Ch 5 'Refraction through a Lens' (aplustopper.com extract)_
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