Why can a real optical image be projected onto a screen?

A real optical image can be projected onto a screen because, unlike a virtual image, the light rays forming a real image are physically brought to a focus at the image position.1

In an optical system, such as a lens or a mirror, light waves originating from an object are refracted or reflected such that they converge at a specific point or plane in space. Because these rays actually intersect at the image location, they can be intercepted by a physical surface—such as a sheet of paper or a projection screen—making the image visible to an observer.12

Common examples of this phenomenon include the images captured by a camera lens on film or those cast by a projector onto a screen. Conversely, virtual images cannot be projected because they are formed by rays that do not actually converge at the location where the image appears to be.13