Some ray diagrams may also show a third ray. Peep holes contain concave lenses. They are set into doors so the occupant can identify a visitor before opening the door.

A stunning new image from the James Webb Space Telescope (JWST) is allowing astronomers to examine the complex and turbulent ...

A joint Chinese and European X-ray telescope mission called Einstein Probe is successfully viewing the universe in widescreen, with a telescope design that mimics the eyes of lobsters. Einstein ...