A plano-concave lens is a lens with one side being flat and the other side being concave. It is characterized by being thin in the center and thick at the edges, and can make parallel light rays ...

Definition: An achromatic lens can be defined as a lens which is made by a combination of two different types of lenses carrying different focal powers in a manner such that the images formed by the ...

Fingerprints, water stains, oils from your face — we live in a world of smudges. Lucky for you, we also live in a world of small, convenient items designed to make life easier. Whether you’re cleaning ...

What do you notice about the mass of biological (living) forms and mass of technological (man-made) forms on Earth? What do you wonder? By The Learning Network A teenager and a New York Times ...