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 invented is the optical microscope. The name of this inventor is hard to pin down. The first compound microscope appeared in the Netherlands by the 1620s, maybe the inventor was Cornelis Drebbel. Galileo Galilei had a compound microscope in 1625 which he called the little eye.