When an object, such as a pencil, is partly immersed in water and viewed from above, it appears to bend underwater. This illusion is caused by refraction, the change in direction of a wave as it leaves one medium and enters another. Waves travel with greater velocity in some media than in others, and when a wave enters a new medium at a certain angle, the change in speed occurs sooner on one side of the wave than on the other. What other optical phenomena are caused by refraction?
Back in the day
In 1981, Pope John Paul II was shot in Vatican City's St. Peter's Square by Turkish terrorist Mehmet Ali Agca, who was captured and imprisoned. Although the pontiff was shot in the stomach, he recovered and publicly forgave his would-be assassin. In spite of the physical setback caused by the shooting, he continued to travel widely, eventually visiting 129 nations and increasing the international character of the papacy. What now marks the site of the shooting in St. Peter's Square?
Born on a day like today
An influential Indianapolis preacher, Jones formed the People's Temple in 1955. After he became the subject of criminal investigations, particularly regarding his alleged diversion of cult members' donations for his personal use, he and about 1,000 followers relocated to Jonestown, Guyana, in 1977. In 1978, cult members killed US Representative Leo Ryan and four others during an investigatory visit. The next day, Jones orchestrated the mass murder-suicide of how many of his followers?