Question 1. Sketch the letter e in the circle on the summary chart jus at it app

Question

Question 1. Sketch the letter e in the circle on the summary chart jus at it appears in the field( the area you see through the microscope). how far is the bottom of the objective lens from the surface of the slide? In other words, what is the working distance? use a millimeter ruler to make this measurement. record the working distance in the summary chart. How has the apparent orientation of the e changed top to bottom, right to left, and so on?

Question 2. Move the slide slowly away from you on the stage as you view it through the ocular lens. In what direction does the image move?

Question 3. Move the slide to the left. In what direction does the image move?

Question 4. Today, most good laboratory microscopes are parfocal; that is, the slide should be in fous ( or nearly so) at the higher magnifications once you have properly focused at the lower magnification. Without touching the focusing knobs, increase the magnification by rotating the next higher magnification lens into position over the stage. Make sure it clicks into positioin. Using the fine adjustment only, sharpen the focus. if you are unable to focus with a new lens, your microscope is not parfocal. Do not try to forces the lens into position. Consult your instructor. Note the decrease in working distance. As you can see, focusing with the coarse adjustment knob could drive the objective lens through the slide, breaking the slide and possibly damaging he lens. Sketch the letter e in the summary chart. What new details become clear?

Question 5. As best you can, measure the distance between the objective and the slide. Record the working distance in the summary chart. Is the image larger or smaller?

Question 6. Approximately how much of the letter e is visible now?

Question 7. Is the field larger or smaller?

Question 8. Why do your cheek cells look different from those illustrated in figure 3.5? ( Hint: What did you have to do to your cheek to obtain them?)

Question 9. Why are these cells more similar to those seen in Figure 3.5 and easier to measure than those of the wet mount?

Explanation / Answer

1. Working distance is defined as the distance from the front lens element of the objective to the closest surface of the coverslip when the specimen is in the sharp focus. working distance for different objective lens are different. Working distance in milimeter for 4x it is 12.7mm, for 20x it is 15mm, for 25x it is 25.4mm, for 100x it is 60.3mm.

2. As we move slide away from us the slide will go towards bottom of the microscope and the image will move towards us. The working distance will increase.

3. If we move the slide towards left the image will move towards right.

8. To obtain cheek cells first take a cotton swab and scrape inside the mouth. Smear the cotton swab on the center of the micrmicroscopic slide. Add few methylene blue drops and place a cover slip on it and watch under microscope.

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