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Question

Parts of the following:

a) Magnifying parts of a microscope

b) illuminating parts of a microscope

c) Mechanical parts of a microscope

Answer 1

[edit] The components of the microscope



Basic optical microscope elements(1990's)

Basic optical microscope elements(1900's):

1. ocular lens, or eyepiece

2. objective turret

3. objective lenses

4. coarse adjustment k**b

5. fine adjustment k**b

6. object holder or stage

7. mirror

8. diaphragm and condenserAll optical microscopes share the same basic components:

The eyepiece - a cylinder containing two or more lenses to bring the image to focus for the eye. The eyepiece is inserted into the top end of the body tube. Eyepieces are interchangeable and many different eyepieces can be inserted with different degrees of magnification. Typical magnification values for eyepieces include 5x, 10x and 2x. In some high performance microscopes, the optical configuration of the objective lens and eyepiece are matched to give the best possible optical performance. This occurs most commonly with apochromatic objectives.

The objective lens - a cylinder containing one or more lenses to collect light from the sample. At the lower end of the microscope tube one or more objective lenses are screwed into a circular nose piece which may be rotated to select the required objective lens. Typical magnification values of objective lenses are 4x, 5x, 10x, 20x, 40x, 80x and 100x. Some high performance objective lenses may require matched eyepieces to deliver the best optical performance.

The stage - a platform below the objective which supports the specimen being viewed. In the center of the stage is a circular hole through which light passes to illuminate the specimen. The stage usually has arms to hold slides (rectangular glass plates with typical dimensions of 25 mm by 75 mm, on which the specimen is mounted).

The illumination source - below the stage, light is provided and controlled in a variety of ways. At its simplest, daylight is directed via a mirror. Most microscopes, however, have their own controllable light source that is focused through an optical device called a condenser, with diaphragms and filters available to manage the quality and intensity of the light.

The whole of the optical assembly is attached to a rigid arm which in turn is attached to a robust U shaped foot to provide the necessary rigidity. The arm is usually able to pivot on its joint with the foot to allow the viewing angle to be adjusted. Mounted on the arm are controls for focusing, typically a large knurled wheel to adjust coarse focus, together with a smaller knurled wheel to control fine focus.

Updated microscopes may have many more features, including transmission illumination, phase contrast microscopy and differential interference contrast microscopy, and digital cameras.

On a standard compound optical microscope, there are three objective lenses: a scanning lens (4×), low power lens (10×)and high power lens (40×). Advanced microscopes often have a fourth objective lens, called an oil immersion lens. To use this lens, a drop of immersion oil is placed on top of the cover slip, and the lens is very carefully lowered until the front objective element is immersed in the oil film. Such immersion lenses are designed so that the refractive index of the oil and of the cover slip are closely matched so that the light is transmitted from the specimen to the outer face of the objective lens with minimal refraction. An oil immersion lens usually has a power of 100×.

The actual power or magnification of an optical microscope is the product of the powers of the ocular (eyepiece), usually about 10×, and the objective lens being used.

Compound optical microscopes can produce a magnified image of a specimen up to 1000× and, at high magnifications, are used to study thin specimens as they have a very limited depth of field.