Optics 1 Question 6

6. 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 $P A$. When the student shifts his/her eye towards left, the image appears to the right of the object pin. Then

(2007, 3M)

(a) $x<f$

(b) $f<x<2 f$

(c) $x=2 f$

(d) $x>2 f$

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Answer:

Correct Answer: 6. (b)

Solution:

  1. 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 $f<x<2 f$.



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