Explanation:

- An image visible on a screen is called a real image. A real image occurs when light rays actually converge at a point.

- Conversely, the image formed by a plane mirror is a virtual image. This happens as the light rays do not actually meet but appear to diverge from a point behind the mirror.

- Option 1, "real; virtual," accurately describes these phenomena.

- Option 2, "parabolic; perpetual," involves unrelated terms. Parabolic relates to curves, while perpetual is about ongoing states.

- Option 3, "virtual; real," is incorrect as it reverses the definitions.

- Option 4, "vector; layered," misuses technical terms unrelated to optics.