A thin rod of length 10 cm is placed along the principal axis of a concave mirror of focal length = 30 cm such that its image, which is real and elongated, just touches the rod. Find the length (in cm) of the image?
Options

Question

A thin rod of length 10 cm is placed along the principal axis of a concave mirror of focal length = 30 cm such that its image, which is real and elongated, just touches the rod. Find the length (in cm) of the image?

Options

G1 Physics · Accepted Answer

Derived solution: Step 1: Use the spherical-mirror relation 1/f = 1/v + 1/u with m = - v/u and R = 2f, following the Cartesian sign convention. Step 2: Substitute the values given in the question and apply the geometry/sign convention shown. Step 3: On simplification the result is 15. Therefore the correct option is C.