Question Detail
Question
A concave mirror of radius curvature 20 cm has an object placed 20 cm from it. Determine the distance of the image formed from the mirror.
Correct Answer
Option B is the correct answer.
Detailed Explanation
For a concave mirror, the focal length (f) is half the radius of curvature (R).f = R/2 = 20 cm / 2 = 10 cm.The mirror formula is 1/f = 1/u + 1/v, where 'u' is the object distance and 'v' is the image distance.Given u = 20 cm and f = 10 cm.1/10 = 1/20 + 1/v1/v = 1/10 - 1/201/v = (2 - 1)/201/v = 1/20v = 20 cm.This means the object is placed at the center of curvature (C), and the image is also formed at the center of curvature, real and inverted.
Hint
Recall the relationship between focal length and radius of curvature for a spherical mirror. Also, consider the special case when an object is placed at the center of curvature of a concave mirror.