Question

In an experiment to determine the focal length $f$ of a concave mirror by the $\text{u}-\upsilon$ 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

• A. $x<\text{f}$
• B. $\text{f}<x<2\text{f}$
• C. $x=2\text{f}$
• D. $x>2\text{f}$

Answer 1

Answer: (B)

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 $\text{f}<x<2\text{f}$ .

$\therefore$ Correct option is $(b)$