Q. Two thin lenses of focal lengths f₁ and f₂ are in contact and coaxial. The power of the combination is
A) (f₁ + f₂)/(f₁f₂)
B) √(f₁/f₂)
C) √(f₂/f₁)
D) (f₁ + f₂)/2
Explanation
[Solution from source] For thin lenses in contact, powers add: P = 1/f₁ + 1/f₂ = (f₁ + f₂)/(f₁f₂). (f₁ + f₂)/2 has dimensions of length, so it cannot be a power. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.