The objective on a microscope is comprised of a tube and one or more lenses, and may include a mirror as well. Its purpose is to gather and focus light,Most microscopes have four objective lenses, and each provides a varying level of magnification. The shortest objective possesses the least power (4X), and is called the scanning objective. It is followed by the low power objective (10X) and the high power objective or “high-dry” objective (40X). The longest objective, which is also the strongest, is the oil immersion objective (100X). The maximum magnification potential of an objective lense is typically determined by its distance from the image plane and the specimen that’s being observed. scanning objective – for locating the specimen on the slide (= low power objective)
high power objective – magnifies the specimen to provide a detailed image coarse adjustment – used to focus the image when using low power diaphragm – used to adjust the amount of light passing through the specimen revolving nosepiece – holds the three objective lenses – it can be rotated to change the objective in use arm – holds the stage and the lens system – can be used to tilt the microscope (but not advised) substaGe lamp – provides a uniform illumination (more reliable than daylight !!)
The objective lenses are the primary lenses in a microscope. Other lenses help provide illumination or additional fine focus, but it is the objective lens that provides the majority of the image enhancement. According to Professor John Rodenburg of the University of Sheffield, the objective lens is typically considered to be the most important lense in any microscopic equipment.
The objective lens in a microscope is the lens that is closest to the specimen being magnified. Although there are many lenses in the microscope, each of which performs a different type of function, it is the objective lens that contributes the most to enhancing the detail of the specimen. Most microscopes have three or four objective lenses. Each objective lens provides a different level of magnification. The longest lens possesses the greatest magnification power. Since the objective lens is closest to the specimen, it is the farthest from the eye of the observer and provides the greatest magnification.
The objective lens strengths found in most microscopes are the 4x, 10x, 40x and 100x. To calculate the actual magnification provided by each type of objective lens, simply multiply the number before the x by ten. Thus a 4x lens actually shows an object at 40 times its natural size. 10x lenses show an object at 100 times, a 40x at 400 times, and a 100x at 1,000 times magnification.
The magnification potential of the objective lens is determined by the ratio between its distance from both the specimen and the image plane. The image plane is where we actually observe the magnified image. For most standard microscopes the image plane is in the eye pieces through which you look. More sophisticated microscopic equipment may also feature a projector which casts the image onto a separate surface. Here it is the focal point from which the image is projected that constitutes the image plane, rather than the eye pieces.
