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.
The first microscope was made around 1595 in Middelburg, Holland. Three different eyeglass makers have been given credit for the invention: Hans Lippershey (who also developedâ¦ the first real telescope); Hans Janssen; and his son, Zacharias. The coining of the name microscope has been credited to Giovanni Faber, who gave that name to Galileo Galilei's compound microscope in 1625.