what is the function of objective lens in microscope
Objective (optics) The objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass, with very short focal length. This is brought very close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube. The objective itself is usually a cylinder containing one or more lenses that are typically made of glass; its function is to collect light from the sample.
Optical microscope A compound microscope uses a lens close to the object being viewed to collect light (called the objective lens) which focuses a real image of the object inside the microscope (image 1). That image is then magnified by a second lens or group of lenses (called the eyepiece) that gives the viewer an enlarged inverted virtual image of the object (image 2).[5] The use of a compound objective/eyepiece combination allows for much higher magnification. Common compound microscopes often feature exchangeable objective lenses, allowing the user to quickly adjust the magnification.[5] A compound microscope also enables more advanced illumination setups, such as phase contrast.
Microscope Although objects resembling lenses date back 4000 years and there are Greek accounts of the optical properties of water filled spheres (5th century BC) followed by many centuries of writings on optics, the earliest known use of simple microscopes (magnifying glasses) dates back to the widespread use of lenses in eyeglasses in the 13th century.[2][3][4] The earliest known examples of compound microscopes, which combine an objective lens near the specimen with an eyepiece to view a real image, appeared in Europe around 1620.[5] The inventor is unknown although many claims have been made over the years. Several revolve around the spectacle making centers in the Netherlands including claims it was invented in 1590 by Zacharias Janssen (claim made by his son) and/or Zacharias' father, Hans Martens,[6][7] claims it was invented by their neighbor and rival spectacle maker, Hans Lippershey (who applied for the first telescope patent in 1608),[8] and claims it was invented by expatriate Cornelis Drebbel who was noted to have a version in London in 1619.[9][10] Galileo Galilei (also sometimes cited as compound microscope inventor) seems to have found after 1610 that he could close focus his telescope to view small objects and, after seeing a compound microscope built by Drebbel exhibited in Rome in 1624, built his own improved version.[11][12][13] Giovanni Faber coined the name microscope for the compound microscope Galileo submitted to the Accademia dei Lincei in 1625 [14] (Galileo had called it the "occhiolino" or "little eye").
Microscope Although objects resembling lenses date back 4000 years and there are Greek accounts of the optical properties of water-filled spheres (5th century BC) followed by many centuries of writings on optics, the earliest known use of simple microscopes (magnifying glasses) dates back to the widespread use of lenses in eyeglasses in the 13th century.[2][3][4] The earliest known examples of compound microscopes, which combine an objective lens near the specimen with an eyepiece to view a real image, appeared in Europe around 1620.[5] The inventor is unknown although many claims have been made over the years. Several revolve around the spectacle-making centers in the Netherlands including claims it was invented in 1590 by Zacharias Janssen (claim made by his son) and/or Zacharias' father, Hans Martens,[6][7] claims it was invented by their neighbor and rival spectacle maker, Hans Lippershey (who applied for the first telescope patent in 1608),[8] and claims it was invented by expatriate Cornelis Drebbel who was noted to have a version in London in 1619.[9][10] Galileo Galilei (also sometimes cited as compound microscope inventor) seems to have found after 1610 that he could close focus his telescope to view small objects and, after seeing a compound microscope built by Drebbel exhibited in Rome in 1624, built his own improved version.[11][12][13] Giovanni Faber coined the name microscope for the compound microscope Galileo submitted to the Accademia dei Lincei in 1625[14] (Galileo had called it the "occhiolino" or "little eye").