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diffraction

(Encyclopedia)diffraction, bending of waves around the edge of an obstacle. When light strikes an opaque body, for instance, a shadow forms on the side of the body that is shielded from the light source. Ordinarily...

Claudius I

(Encyclopedia)Claudius I (Tiberius Claudius Drusus Nero Germanicus) klôdˈēəs [key], 10 b.c.–a.d. 54, Roman emperor (a.d. 41–a.d. 54), son of Nero Claudius Drusus Germanicus and thus nephew of Tiberius. When...

hibernation

(Encyclopedia)hibernation hīˌbərnāˈshən [key] [Lat.,= wintering], practice, among certain animals, of spending part of the cold season in a more or less dormant state, apparently as protection from cold when ...

gills, in biology

(Encyclopedia)CE5 Gills of a fish: Side view (A) and ventral view (B) gills, external respiratory organs of most aquatic animals. In fishes the gills are located in gill chambers at the rear of the mouth (phary...

Geiger counter

(Encyclopedia)Geiger counter or Geiger-Müller (G-M) counter gīˈgər-mŭlˈər, –myo͞oˈlər [key], instrument for the detection and quantitative determination of ionizing radiation such as the alpha and beta ...

John I, king of Hungary

(Encyclopedia)John I (John Zapolya) zäˈpôlyŏ [key], 1487–1540, king of Hungary (1526–40), voivode [governor] of Transylvania (1511–26). He was born John Zapolya, the son of Stephen Zápolya. The leader of...

Polish Succession, War of the

(Encyclopedia)Polish Succession, War of the, 1733–35. On the death (1733) of Augustus II of Poland, Stanislaus I sought to reascend the Polish throne. He was supported by his son-in-law, Louis XV of France. The r...

pupa

(Encyclopedia)pupa pyo͞oˈpə [key], name for the third stage in the life of an insect that undergoes complete metamorphosis, i.e., develops from the egg through the larva and the pupa stages to the adult. A compl...

Lewis and Clark expedition

(Encyclopedia)Lewis and Clark expedition, 1803–6, U.S. expedition that explored the territory of the Louisiana Purchase and the country beyond as far as the Pacific Ocean. The men were gathered and in the winte...

Afghanistan

(Encyclopedia)CE5 Afghanistan ăfgănˈĭstănˌ, ăfgänˌĭstänˈ [key], officially Islamic Republic of Afghanistan, republic (2020 est. pop. 38,930,000), 249,999 sq mi (6...