In an experiment to determine the focal length `(f)` of a concave mirror by the `u-v` 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

A. `x lt f`
B. `f lt x lt 2f`
C. `x =2 f`
D. `x gt2f`

Answer

b.

Explanation

Since object and image move in opposite direction, the positioning should be as shown in the figure. Object lies between focus and center of curvature, `f lt x lt 2f`.
`:.` Correct option is (b).