Q9. A normal eye has a near point at 25 cm. A converging lens of power +2 D is placed very close to the eye. The closest object that can be viewed clearly through the lens is:
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Question

Q9. A normal eye has a near point at 25 cm. A converging lens of power +2 D is placed very close to the eye. The closest object that can be viewed clearly through the lens is:

G1 Physics · Accepted Answer

GIVEN: Eye near point D = 25 cm; extra converging lens power +2 D. Step 1: Focal length f = 1/P = 1/2 m = +50 cm. Step 2: The closest visible object must be imaged virtually at the eye's 25 cm near point: v = −25 cm. Step 3: Let u = −x. Lens formula: 1/50 = −1/25 + 1/x. Step 4: 1/x = 1/50 + 1/25 = 1/50 + 2/50 = 3/50. Step 5: x = 50/3 = 16.666… cm. FINAL ANSWER: 16.67 cm. Option B.