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.
Simple Answer: The inventor of the first microscope is not recorded. The simple single-lens form of a microscope was in use by the 13th century by some accounts. The modern compound microscope was first developed in 1590 by the Dutch spectacle-makers Hans Janssen and his son Zacharias Janssen.More: The first microscope was merely a single lens.t is thought that around 1,000 AD use of the lens as a magnifying device was established, to this may be considered the time of the first microscope. The invention of the first lenses in spectacles to improve vision was in Italy in the 13th century.