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Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection. In acoustics, reflection causes echoes and is used in sonar...

Street art is any art developed in public spaces — that is, "in the streets" — though the term usually refers to unsanctioned art, as opposed to government sponsored initiatives. The term can include traditional graffiti artwork, sculpture, stencil graffiti, sticker art, wheatpasting and street poster art, video projection, art intervention, guerrilla art, flash mobbing and street installations...

Cyclocosmia is a genus of spiders in the Ctenizidae family. The abdomen of spiders in this genus is abruptly truncated and ends in a hardened disc which is strengthened by a system of ribs and grooves. They use this to clog the entrance of their 7 to 15 cm deep vertical burrows when threatened, a phenomenon called phragmosis. Strong spines are located around the edge of the disc. The four spinnerets are found just anterior to it, with the posterior, retractable spinnerets particularly large...

An amazing series of high speed photographs created by Scott Linstead. Scott Linstead is an internationally published, freelance wildlife photographer/writer. His clients include Natural History Magazine, Hewlett Packard, Ranger Rick Magazine and a number of wildlife publications in North America and Europe. Scott's column on the techniques of bird photography appears in every issue of Outdoor Photography Canada...

A puppy is a juvenile dog. Some puppies may weigh 1–3 lb (0.45–1.4 kg), while larger ones can weigh up to 15–23 lb (6.8–10 kg). All healthy puppies grow quickly after birth. A puppy's coat color may change as the puppy grows older, as is commonly seen in breeds such as the Yorkshire Terrier. In vernacular English, puppy refers specifically to dogs while pup may often be used for other mammals such as seals, giraffes, guinea pigs, or even rats...

These photos of American kids were taken in the early 20th century. It looks like most of them were already working and smoking. Young people were involved in all the crucial episodes of American history: They sailed with Columbus; served as go-betweens for English colonists and Indians; toiled as indentured servants; were kidnapped into slavery; fought in the Revolution and the Civil War; labored in coal mines and factories; and stood at the forefront of the Civil Rights movement...