Question

. A concave mirror has a focal
length of 4cm. At which of the
following distance should an
object be placed so that it may
form virtual, erect and
magnified image?​

Answer 1

Answer:

The relationship between the radius of curvature and focal length is that the radius of curvature is twice the focal length.

In this case, focal length of the concave mirror is given as 15 cm. Hence, the radius of curvature is 15×2=30 cm.

When the object is placed on the centre of curvature, on the principal axis, in front of a concave lens, the image is formed at the same point. The image formed is real and inverted.

So, in this case, the object distance is equal to the image distance.

Therefore, the object size is equal to the image size.