An object is placed at a distance of 15 cm in front of a concave mirror with a radius of curvature of 20 cm. Which one among the following statements is correct for the image formed?
A.The image is 30 cm from the mirror on the same side as the object.✓ Correct
B.The image is formed at a distance of 30 cm behind the mirror.
C.The image is 60 cm from the mirror on the same side as the object.
D.The image is formed at a distance of 60 cm behind the mirror.
Explanation
For a concave mirror, focal length f = R/2 = 20/2 = 10 cm. Using the mirror formula 1/v + 1/u = 1/f with the sign convention u = −15 cm and f = −10 cm: 1/v = 1/f − 1/u = (−1/10) − (−1/15) = −1/10 + 1/15 = (−3 + 2)/30 = −1/30, so v = −30 cm. The negative sign indicates the image is formed on the same side as the object (in front of the mirror), i.e., it is a real, inverted image at 30 cm from the mirror. Hence option (a) is correct.
💡 Practice unlimited CDS PYQs + AI-tracked progress on each topic. Sign up free →