Because the objective lens is a positive lens, it inverts the image before it projects it to the ocular lens the lens closest to the eye. The image formed by the objective lens is inverted because the rays that are projected through the light cross over, causing the image to appear upside down.
Because the ocular lens is a simple magnifying lens, it does not correct the flipped image, and thus the specimen appears inverted when the image reaches the eye. In this test, a doctor takes a small sample of cells from the uterine cervix of a patient and sends it to a medical lab where a cytotechnologist stains the cells and examines them for any changes that could indicate cervical cancer or a microbial infection.
They are trained to determine which cellular changes are within normal limits and which are abnormal. Their focus is not limited to cervical cells; they study cellular specimens that come from all organs. When they notice abnormalities, they consult a pathologist, who is a medical doctor who can make a clinical diagnosis.
A cell is the smallest unit of life. Most cells are so tiny that they cannot be seen with the naked eye. Therefore, scientists use microscopes to study cells. Electron microscopes provide higher magnification, higher resolution, and more detail than light microscopes. The unified cell theory states that all organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells.
Skip to main content. Cellular Structure. Search for:. Reading: Microscopy Cells vary in size. This real image is inverted at the focal length. An example of this is using a letter of the alphabet. When the letter "e" is put right-side up in the slide to the observer, it is projected upside down in the tube.
Moving the slide to the right shifts the image to the left, and vice versa. The ocular lens , or eyepiece lens, acts as a magnifying glass for this real image. The ocular lens makes the light rays spread more, so that they appear to come from a large inverted image beyond the objective lens. Because light rays do not actually pass through this location, the image is called a virtual image. The most important consideration for image formation with the objective lens other than its magnification or power is its numerical aperture.
This is a number that is directly related to the resolving power of the objective. It is a critical aspect in obtaining a useful microscopic image.
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