STANDARD Physics Lens Combination MCQ Question
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
10 cm
20 cm
40 cm
infinity
Correct Answer
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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