Question

30. The image of an object placed at 24cm in front of a lens is obtained on a screen at a distance of 72cm
from it. Calculate the focal length of the lens. What should be the height of the image if the object is
2.0cm high? Draw the ray diagram corresponding to this case.​

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.

As the object is of 4 cm in length, the image will also be of 4 cm in length.