This video features a device that uses a concave mirror to project the image of a small light bulb into an empty light socket. While it is possible to hide the source of the projected light from the viewers, I have found it better to allow students to easily see the source of the hidden light for a better understanding of the behavior of light rays reflected by a concave mirror.
The question arises if the image is a real or a virtual image. Let’s start with real images are always inverted and virtual images are always upright A real image is one on the same side of the lens or mirror as the viewer, whereas a virtual image is one on the opposite side of the lens or mirror.
In optics, a virtual image is an image formed when the outgoing rays from a point on an object always diverge. The image appears to be located at the point of apparent divergence. Because the rays never converge, a virtual image cannot be projected onto a screen.
In contrast, a real image is one that is formed when the outgoing rays from a point converge at a real location. Real images can be projected onto a diffuse reflecting screen, but a screen is not necessary for the image to appear. The point is, a screen is not required for a real image but can be a test for a real image.
For example, holograms are real images, the idea is to produce an image that appears in the air. There is a popular toy called mirage that projects the image of object apparently floating above the mirror. It is a 3 dimensional 3-D real image.