Question

critical thinking and review questions

1. match the part of the microscope to the description on the right.

condenser a. move the slide
coarse - adjustment knob b. used for precise focusing
stage controls c. used for general focusing
fine - adjustment knob d. have different magnifications
objective lenses e. focuses light on the specimen

1. what is the total magnification if the ocular lens is 10× and the objective lens is 100×?

show the calculations.

1. why should you scan a specimen under scanning power before using higher magnifications?
2. after focusing on the top of the specimen, what happens to the depth of focus as you

turn the fine adjustment knob backward?

1. how is poor light quality affected by opening the iris diaphragm?
2. summarize the procedure for preparing a wet mount slide.
3. briefly describe how to put away and store your microscope.

Explanation:

1. Matching: Matches each microscope part to its core function based on standard microscope terminology.
2. Total Magnification: Calculated by multiplying the magnification of the ocular (eyepiece) lens and the objective lens, the standard method for total magnification in light microscopes.
3. Scanning Power Rationale: Scanning power (low magnification) provides a wide field of view to locate the target specimen area, which is then centered and magnified further; high magnification has a very narrow field of view, making locating specimens directly difficult.
4. Depth of Focus: The fine adjustment knob moves the stage (or objective lens) slightly. Turning it backward moves the lens away from the specimen, increasing the depth of focus to reveal structures below the top surface.
5. Iris Diaphragm & Light Quality: The iris diaphragm controls the amount of light passing through the specimen. Opening it lets in more light, which improves visibility and resolves poor, dim light quality.
6. Wet Mount Procedure: Summarizes the standard, step-by-step process for preparing a temporary wet mount slide for microscopy.
7. Microscope Storage: Outlines the proper, standard steps to clean and store a microscope to maintain its condition.

Answer:

1. - Condenser: e. focuses light on the specimen

• Course-adjustment knob: c. used for general focusing
• Stage controls: a. move the slide
• Fine-adjustment knob: b. used for precise focusing
• Objective lenses: d. have different magnifications

1. Total magnification = Ocular lens magnification × Objective lens magnification

$\text{Total magnification} = 10\times \times 100\times = 1000\times$

1. Scanning power (low magnification) provides a wide field of view to easily locate the specimen. High magnification has a very narrow field of view, so it is hard to find the specimen directly at high power.
2. Turning the fine adjustment knob backward increases the depth of focus, allowing you to focus on structures located below the top surface of the specimen.
3. Opening the iris diaphragm lets in more light, which improves poor light quality by making the specimen brighter and more visible, enhancing focus clarity.
4. 1. Place a small drop of liquid (containing the specimen) in the center of a clean glass slide.
5. Use forceps to hold a coverslip by its edge, lower one edge into the liquid drop, then slowly lower the rest to avoid air bubbles.
6. Blot away any excess liquid from the edge of the coverslip with absorbent paper.
7. 1. Clean all objective lenses and the ocular lens with lens paper (use lens cleaner only if necessary, following proper technique).
8. Lower the stage completely, and rotate the lowest power (scanning) objective lens into place.
9. Turn off the light source, unplug the microscope, and wrap the cord neatly.
10. Replace the dust cover over the microscope.
11. Carry the microscope by holding its arm and supporting the base, then place it in its designated storage location.