Q. 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 principle 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) $x < f$
B) $f < x < 2f$
C) $x = 2f$
D) $x > 2f$
Explanation
(b) Since object and image move in opposite directions, the positioning should be as shown in the figure. Object lies between focus and center of curvature $f < x < 2f.$
[image:9_image99.jpeg]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.