A person is viewing an extended object. If a converging lens is placed in front of his eye, will he feel that the size of object has increased? Why?

If a convex lens is placed in front of eye then it will act as a dual convex lens.

The ray diagram would be like as shown in figure of microscope. Take the eyepiece as our eye. The light rays from the extended source strikes the objective lens and after refraction it will converge at beyond the focal length of eyepiece. This image will act as an object of the eyepiece which is able to accommodate its focal length according to the distance of the object and thus the final image formed is enlarged & inverted.

Thus the person will be able to see an enlarged image of the object.