An object is placed in front of a convex lens of focal length . At what distance from the lens (in cm) is the image formed?
Answer and explanation
Correct answer: B. 120
- Step 1: Apply the thin lens formula with standard Cartesian sign conventions.
- Step 2: Assign given parameters: object distance and focal length for a converging convex lens : .
- Step 3: Rearrange and solve for image distance : .
Answer
120.
Why not the others: The other values (120/7, 130, 70) stem from violating Cartesian sign conventions for focal length and object distance, or adding reciprocals incorrectly.
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