A convex lens has a focal length of 15 cm. At what distance should an object be placed in front of the lens to get a real image of the same size of the object ?
15 cm
10 cm
30 cm
40 cm
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC CDS-1 – 2022
For a convex lens, a real image of the same size as the object is formed when the object is placed at a distance equal to twice the focal length (2f) from the lens. At this position (often referred to as 2F or C), the image is also formed at a distance of 2f on the opposite side of the lens, and it is real, inverted, and of the same size as the object. Given the focal length (f) is 15 cm, the object distance required is 2 * f = 2 * 15 cm = 30 cm.