Microscopy

Q1: Which adjustment knob should you use with the 4x (scanning) objective lens?
A1: Use the coarse adjustment knob (the larger knob).

Q2: Which adjustment knob should you use with the 10x (low power) and 40x (high power) objective lenses?
A2: Use the fine adjustment knob (the smaller knob).

Q3: Why should you never use the coarse adjustment knob with the high power (40x) or oil immersion (100x) lenses?
A3: You may accidentally crack the slide or damage the lens due to the small working distance.

Steps to Focus the Microscope

Q4: What is the first step in focusing a microscope?
A4: Click the scanning lens (4x) into position.

Q5: How should you position the slide on the stage?
A5: Center the slide on the stage, ensuring the area of interest is over the light source, and secure it with the slide clamp.

Q6: What should you do before looking through the ocular lenses to focus?
A6: Raise the stage as high as it will go to maximize the working distance.

Q7: How do you adjust the ocular lenses for your eyes?
A7: Cover one eye, focus with the coarse and fine knobs using the other eye, then adjust the focus of the second ocular lens using its knob.

Q8: What does it mean if a microscope is "parfocal"?
A8: It means you can switch between objective lenses with only minor adjustments using the fine focus knob.

Working Distance and Depth of Field

Q9: What is "working distance" in microscopy?
A9: The distance between the tip of the objective lens and the slide. It decreases with higher magnification.

Q10: Why should you always start focusing with the 4x lens?
A10: It has the greatest working distance, reducing the risk of crashing the lens into the slide.

Q11: What happens to the depth of field as magnification increases?
A11: The depth of field decreases, meaning only a thin horizontal plane will be in sharp focus.

Q12: What is a sign that you’ve made a mistake while focusing?
A12: The sound of crunching glass, indicating a damaged lens or broken slide.

Magnification

Q13: How do you calculate total magnification?
A13: Multiply the magnification of the objective lens by the magnification of the ocular lens (e.g., 4x objective × 10x ocular = 40x total magnification).

Q14: Where is the magnification of the objective lens indicated?
A14: It is inscribed on the lens barrel (e.g., EA10 for the 10x lens).

Q15: What is the total magnification if you use the 40x objective lens and a 10x ocular lens?
A15: 40 × 10 = 400x magnification.

Estimating the Size of Objects

Q16: What is the "field of view" in microscopy?
A16: The diameter of the circle of light you see when looking through the microscope.

Q17: How does the field of view change with higher magnification?
A17: The field of view becomes smaller as magnification increases.

Q18: If an object takes up half the field of view under the 10x lens (1600 microns), how large is the object?
A18: 1600 microns ÷ 2 = 800 microns.

Q19: If an object is one-fifth the diameter of the field of view under the 10x lens (1600 microns), how large is the object?
A19: 1600 microns ÷ 5 = 320 microns.

Microscope Movement and Orientation

Q20: How does the movement of the stage appear through the microscope?
A20: The direction of movement is reversed (e.g., moving the stage to the right makes the object appear to move left).

Q21: What should you use to move the stage?
A21: Use the knobs located under the stage to move it left/right or toward/away from you.

Additional Tips

Q22: When should you adjust the light intensity and iris diaphragm?
A22: After initially focusing the specimen, adjust the light intensity and iris diaphragm for optimal visibility.

Q23: Why should you avoid using the 100x (oil immersion) lens without permission?
A23: It requires immersion oil to focus properly, and improper use can damage the lens.

Q24: What should you do if you encounter a thick slide?
A24: Be extra careful to avoid crashing the objective lens into the slide, especially at higher magnifications.