Compound Light Microscope

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Compound Light Microscope

Compound Light Microscope

Two lens systems are used to enlarge the image in the compound light microscope. There is an 'objective' lens placed near the object on a slide whose image is further magnified by the 'ocular' or 'eye piece'.

The combined magnification capacities of the objective and the eye piece results in the magnified image seen by the unaided eye. If the objective is 10 x and the eye piece is 100x the image will have 10 x 100 = 1000 magnification.

These microscopes carry a condensor lens placed under the slide that focusses light on the specimen making the microscopic field bright. The beam of light can be controlled by a centrifugally operating diagphram.

The resolution limit is dependent on the 'numerical aperture' (NA) which reflects the light-gathering ability of the lens and the wavelength of visible light used. The mathematical equation for arriving at the resolution limit is as follows: Resolution limit = . The best resolution limit can be had by using the shortest wavelength of visible light and an

A. Typical Compound Microscope	B. diagrammatic representation of light paths

a. Ocular

b. Objective

1. Final image at the eye	2. Ocular
3. Objective lens	4. Specimen
5. Condenser lens	6. Field diaphragm
7. Light source	9. Imaging beam path

objective lens Of maximum numerical aperture. The oil immersion objective lens can provide about 1.4 numerical aperture which in combination with blue light of wavelength 0.5 m m, a resolution of about '0.2 m m can be obtained with a compound microscope.

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