Answer: 20 years. Furnaces should last between 15 and 20 years, according to industry experts and the Department of Energy. Furnace filters, however, only hold up one to three months â and in order to avoid an expensive service call, it's crucial to change them on the manufacturer's schedule.
Lens Improvement. Later in the 16th century, Anton van Leeuwenhoek began polishing and grinding lenses when he discovered that certain shaped lenses increased an imageâs size. The glass lenses that he created could enlarge an object many times.
1827 First still photograph taken, using a glass plate technique Claude Niepce's photograph the View from a Window at Le Gras took nearly eight hours to expose. 1832 Joseph Plateau and sons introduce the Phenakistoscope. Like other toys of its kind, the Phenakistoscope was one of the more successful illusion toys.