Using the bright-field compound microscope. 1. Open the iris diaphragm all the w
ID: 102156 • Letter: U
Question
Using the bright-field compound microscope. 1. Open the iris diaphragm all the way while using the low power objective. What happens to the field of view and the quality of the image? Now close the iris diaphragm. What happens to the field of view and the image? 2. Why should you always begin with scanning or low power objective? 3. Why were you asked to use only the fine adjustment knob after switching to 40X? 4. Complete the following table to calculate total magnification for the compound microscope: 5. What is the highest total magnification that can be achieved using the bright-field compound microscope? _____Explanation / Answer
1.iris diaphragm is used to adjust the amount of light that reaches the specimen.
Opening the iris diaphragm will allow increased light to reach the slide and hence better viewing but opening it too far will cause specimen to appear 'washed out' and barely visible..Closing the iris diaphragm will decrease the amount of illumination of specimen but increases the amount of contrast. If iris diaphragm is closed completely the specimen will be too dark to clearly view.
2. Low power objective allows for high resolution , low magnification of an object. You can see the larger details of the object. If we start with low power objective it makes aligning the slide and lens easier. Offers widest field of range. The specimen is easier to locate, center and focus on. Also using low power stage can be raised higher to bring sample closer to eyepiece. After getting the spot to focus on...switch to high power for better focus.
3. When object is in focus use only fine adjustment knob to sharpen the focus. As 40X is a high magnification and any change in focus is much more noticeable.
Using coarse adjustment may drive the lens into the slide and therefore coarse adjustment is used only with low power
(4x, 10x). Also using coarse adjustment will cause the spot to focus pass on.
5. With objective lens of 100x highest magnification is 1000x
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