STANDARDPhysics-Optics
STANDARD Physics Lens Combination MCQ Question
Type: MCQ-conceptual-Medium-Class 12
Two lenses of focal lengths 20 cm and −40 cm are held in contact. The image of an object at infinity will be formed by the combination at
A
10 cm
B
20 cm
C
40 cm
D
infinity
Correct Answer
Option C
Detailed Explanation
The equivalent focal length is given by 1/f = 1/f₁ + 1/f₂. Substituting f₁ = 20 cm and f₂ = −40 cm, we find f = 40 cm. Thus, the image is formed at 40 cm.
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