A thin cylindrical rod of length 10 cm is placed horizontally on the principal axis of a concave mirror of focal length 20 cm. Its midpoint is 40 cm from the pole. The length of the image formed is x/3 cm. The value of x is ______. Image
Physics · Circular Motion
JEE Mains 1 February 2023 Shift 1 Morning Shift

Question

A thin cylindrical rod of length 10 cm is placed horizontally on the principal axis of a concave mirror of focal length 20 cm. Its midpoint is 40 cm from the pole. The length of the image formed is x/3 cm. The value of x is ______. Image

Physics · Circular Motion

JEE Mains 1 February 2023 Shift 1 Morning Shift

G1 Physics · Accepted Answer

The rod ends are at object distances 45 cm and 35 cm. Using mirror formula with f=−20 cm gives image distances v(A)=−36 cm and v(B)=−140/3 cm. Image length = |v(A)−v(B)| = 32/3 cm. Hence x=32.