Question

If the central portion of a convex lens is wrapped in black paper as shown in the figure:

(A) No image will be formed by the remaining portion of the lens.

(B) The full image will be formed but it will be less bright.

(C) The central portion of the image will be missing.

(D) There will be two images each produced by one of the exposed portions of the lens.

Answer 1

Hint: The black paper covered region blocks some light rays entering. This makes a slight difference in the intensity. It reduces the brightness of the image more than usual. So the image formed is complete but less bright.

Complete step-by-step answer:

The light beam passing through the lens undergoes refraction and forms an image on the other side of the lens. When the central part of the lens is covered with black paper it avoids the light ray passing through it to some extent but not completely. As a large number of rays are passing through the lens only a small percentage of the rays are cut off. It does not make any difference in the size and shape of the image. But since small values of light rays are blocked the intensity of the image is slightly reduced than the normal refraction.

Hence, the correct option is B.

Note: The image formed by a convex lens is real and inverted or virtual and erect depending on the position of the object. The image formed by the concave lens on the other hand is always virtual and erect regardless of the position of the object.