Question

What is the size of an image when the position of the object is at \[F\], position of image is at infinity and image formed through a concave mirror?
A) Enlarged
B) Highly enlarged
C) Same size
D) Diminished

Answer 1

Hint: In this question, we have given a concave lens. We have to identify that condition when the image will be formed too big. In a concave lens, there is a condition, in which the image becomes too large as we move towards the lens but clear image is only formed when the object is at the focus point.

Complete solution:
We know that if an object is placed in front of a concave lens at the point \[F\] which is the focus point of the concave lens then the image is formed at the infinity.

In the above diagram, the object is placed at the focus point \[F\]. Then the incident rays from the object incident on the concave lens and after refraction from the concave lens the refracted rays move outside the principal axis. So, the image is formed at infinity. As all the refracted rays are going outwards and there is no limit or boundary. So, the image becomes highly enlarged.

Additional Information:
A concave lens is a lens whose curved faces are curved inwards. While a convex lens is the lens whose curved faces are curved outwards. A concave lens diverges the rays while a convex lens converges the rays.

Note: In this question, we have to remember that the highly enlarged image will be formed when the object is placed at focus point. In a concave lens, as the object is moved towards the lens, the size of the image will increase.