When an object is at a distance of twice the focal length from a concave lens, the image produced is virtual and smaller than the object. what happens to the image if the object is shifted closer to the lens to a point one focal length away from it?

the image produced is virtual and enlarged.
the image produced is virtual and smaller than the object.
the image produced is real and enlarged.
the image produced is real and smaller than the object.
the image produced is virtual and of the same size as the object.

The image produced is virtual and smaller than the object.

Explanation:

For concave lens we know that

here we have

Magnification will be given as

so image will be virtual and formed behind the lens

Now the object position is shifted to new position at distance of focal length

now again we will have

here we have

Magnification will be given as

So again we will have virtual image with magnification 1/2

so here size of image is less than object size by factor of 1/2 and it is virtual

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .