Question

if a biconvex lens is focused towards sun ,a pointed image is formed at 10 cm from the optical centre.find its radius of curvature​

Answer 1

In a BiConvex Lens , if the object is at infinity , the image is formed at focus.

As, the sun is very very far , we consider it at infinity.

So, the image of sun will be formed at focus .

As, focal length is distance of focus from optical centre .

So, focal length of biconvex lens = + 10 cm

Also, Radius of curvature of biconvex lens = 2 * focal length

Thus, Radius of curvature of biconvex lens = 2 * 10 cm

= + 20 cm

Answer 2

Firstly, refer to the image to find out how a bi convex or converging lens looks like. In a biconvex lens, when the object is placed at infinity, the image is formed at the principle focus F, which is half of radius of curvature.

The image formed is real, inverted and highly diminished in this case.

Here, the image is formed at 10 cm away from the optical center O. This means the principal focus F is located at a distance of 10 cm away from the optical center.

We know that the principal focus is located at half the distance away from O as compared to the center of curvature, C.

Therefore, r = 2 f

Hence, radius of curvature = 2 * 10 cm = 20 cm

Hence the answer is 20 cm.