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.
There is a lot of controversy regarding the inventor of compound microscope. Though, there are three contenders-Hans Lippershey, Zacharias Jansen-Hans Janssen and Giovanni Faber who coined the name 'Microscope' for Galileo Galilei's compound microscope in 1625. Galileo used to call it the 'Occhiolino' or 'Little eye'. However, Zacharias Jansen and Hans Janssen are widely regarded as the inventors of compound microscope. Zacharias Jansen was a Dutch spectacle-maker from Middelburg. He is also known as Zacharias Janssen and Sacharias Jansen. During 1590-1595, zaccharias janssen and his son hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged.