Question

………… image cannot be obtained by a convex lens.

Answer 1

You can form real images on just about anything, including convex and concave lenses.

But I think what you meant to ask “what type of image can’t be formed with a convex lens”. You can form both real and virtual images with convex lenses. Consider a camera as an application of the former, and a magnifying glass as an application of the latter.

Answer 2

Answer:

real and enlarged

Explanation:

An image that cannot be obtained on a screen is called a virtual image. Images are of two types: real images and virtual images. Real images are formed on a screen, whereas virtual images cannot be obtained on the screen. Image formed by a convex mirror is always virtual and smaller in size.