THE MICROSCOPE’S STRUCTURE A - Objectives The purpose of the objectives is to create a sharp and contrasting image of the preparation at the magnification displayed. More expensive microscopes usually have objectives that p rovide a better focus throughout the field of vision. They are called semi-plan or plan objectives. Magnifications of 4x, 10x and 40x are common in normal microscopes, and are sufficient for most purposes at p rimary school. 100x objective can be expanded to p rovide a m agnification of 1000x. Used with immersion oil between the objectives and the slide to a chieve the right refraction. Magnification such as this is chiefly used to look at bacteria. B - Eyepiece The purpose of the eyepiece is to enlarge the image c reated by the objectives. All our microscopes come with wide-angle eyepieces with a magnification of 10x. The choice is between microscopes with one or two eyepieces – monocular or binocular m icroscopes. It is much more pleasant to work with binocular microscopes, so you can use both eyes. C - Coarse focus adjustment Used for coarse focus adjustment. More expensive microscopes are provided with better mechanisms that make it easier to turn the knob. D - Focusing. When the coarse and fine settings are on the same rotary knob, setting the microscope requires fewer movements. On the most c ommon microscopes there are two separate rotary knobs. G - Condenser Between the illumination and the stage there is a condenser the purpose of which is to cast the most uniform light on the preparation, and that can be vertically adjusted. The condenser includes an a perture diaphragm that controls the amount of light and the depth of field, and a filter holder whereby filters can be added for further control of brightness and light colour. The simpler microscopes may not have a condenser, and may have a simple pinhole aperture – a disc with holes of different sizes that can be rotated. This only applies to the mini-microscope. B Item no. 076700 A E - Stage E The stage can be solid or floating, or as a cross-plate. On a fixed stage the slide is pushed by hand, with a floating stage the stage is pushed around and with a cross-plate there is a screw that moves the stage in two directions with great accuracy. F - Illumination The illumination can be of different types and strengths. Halogen lamps provide a strong light but develop a great deal G of heat. LED illumination features low power consumption and is suitable for rechargeable m icroscopes, and will take over from halogen illumination in some microsco- F pes. Regulation of the lightstrength is an a dvantage in terms of adapting the amount of light to the magnifi- cation and the density of the preparation. C D 3
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