Question

If the focus of a concave lens is a virtual point, how can a ray appear to come from there? In other words, how can we view the image there?

Answer 1

This is a matter of the way in which your brain interprets the information it receives. It "straightens out" the refracted ray and sees it coming from a point in space behind the lens.

Explanation:

The rays which the eyes detect have been refracted in such a way that they spread out in the real space of the lens, but our brains (in a way that is common to all situations of refraction) interpret the rays as having travelled in a straight line even as they pass through the lens. Thus, they seem to have originated at a point in virtual space, and the brain believes that the object is located at this point, rather than where it actually is. This is true of all images, and explains why the virtual image is seen, as a sort of optical illusion.