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An object is at a distance of 20 m from a convex lens of focal length 0.3 m. The lens forms an image of the object. If the object moves away from the lens at a speed of 5 m/s, the speed and direction of the image will be

Asked in JEE Main 11th Jan 1st Shift 2019 · Lens formula and magnification

• (1) 2.26×10⁻³ m/s away from the lens
• (2) 3.22×10⁻³ m/s towards the lens
• (3) 1.16×10⁻³ m/s towards the lens
• (4) 0.92×10⁻³ m/s away from the lens

Step-by-step solution

Why the other options are wrong

• (1) Gets the direction wrong and makes a numerical slip.
• (2) Gets the direction right but slips in computing (v/u) squared.
• (4) Gets the direction wrong: as the object recedes, the image moves toward the focus.

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