Question

Image formed by a lens of magnification-1. If the distance between object and it's image is 60cm,what is the focal length of the lens? ​

Answer 1

Answer:

The magnification of -1 is possible in only convex lens. When the object is moved 20 cm towards the lens, so the new object distance will be = 30 cm - 20 cm = 10 cm. Since the new object distance is less than focal length of the lens, thus the image will be virtual, erect and magnified. The image will be formed on the same side as that of the object.