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In an experiment to determine the focal length f of a concave mirror by the u - υ method, a student places the object pin A on the principal axis at a distance x from the pole P . The student looks at the pin and its inverted image from a distance keeping his/her eye in line with PA . When the student shifts his/her eye towards left, the image appears to the right of the object pin. Then

Options

  1. Ax < f
  2. Bf < x < 2 f
  3. Cx = 2 f
  4. Dx > 2 f

Correct answer

B. f < x < 2 f

Step-by-step solution

Since object and image move in opposite directions, the positioning should be as shown in the figure. Object lies between focus and centre of curvature f < x < 2 f . ∴ Correct option is ( b )

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