Microscope

What is the purpose of using a microscope in a microbiology laboratory? To magnify microorganisms and other small objects so they can be observed and studied.

What is magnification? Magnification is the process of making an object appear larger so details that cannot normally be seen with the naked eye can be observed.

What is resolution? Resolution is the ability of a microscope to distinguish two objects that are very close together as separate objects. Magnification makes something bigger; resolution makes the image clearer and more detailed.

What is the function of the stage? The stage is the platform that supports the microscope slide.

What is the function of the arm? The arm supports the upper parts of the microscope and is used to carry the microscope safely.

What is the function of the base? The base supports the microscope and provides stability.

What is the function of the substage condenser? The condenser focuses and concentrates light onto the specimen.

What is the function of the iris diaphragm? The iris diaphragm controls the amount of light that passes through the specimen.

What are the typical objective lenses on a compound light microscope and their magnifications? Scanning = 4×; Low-power = 10×; High-power = 40×; Oil-immersion = 100×.

What is the typical magnification of the ocular (eyepiece) lens? 10×

What is the function of the coarse adjustment knob? It makes large movements of the stage or objective to bring the specimen into general focus. Use it mainly with the 4× and 10× objectives, not the 40× or 100× objectives.

What is the function of the fine adjustment knob? It makes very small adjustments to sharpen and clarify the image. Coarse = big focus adjustment; Fine = small/sharp focus adjustment.

What is the function of the light source? It provides the light needed to illuminate the specimen so it can be viewed through the microscope.

How do you calculate total magnification? Total magnification = ocular magnification × objective magnification.

If the ocular lens is 10× and the objective is 40×, what is the total magnification? 10 × 40 = 400×

If the ocular lens is 10× and the oil-immersion objective is 100×, what is the total magnification? 10 × 100 = 1,000×

What is the total magnification when using each objective with a 10× ocular lens? 4× objective → 40× total; 10× objective → 100× total; 40× objective → 400× total; 100× objective → 1,000× total.

What does the word "parfocal" mean? When you switch from one objective lens to another, the specimen should remain nearly in focus and require only a small adjustment with the fine-focus knob.

Why is oil used with the 100× oil-immersion objective? Immersion oil reduces the bending of light between the slide and objective lens, allowing more light to enter the objective and improving resolution.

Which objective lens is used with immersion oil? The 100× oil-immersion objective.

What is the total magnification when using a 10× ocular and a 100× oil-immersion objective? 10 × 100 = 1,000×

What is the basic procedure for focusing a slide using the oil-immersion lens? Begin with 4×; secure the slide; use coarse adjustment to focus; use fine adjustment to sharpen; move to 10× and refocus with fine adjustment; move to 40× and use fine adjustment only; rotate to 100×; place a drop of immersion oil on the slide; move the 100× objective into the oil; use fine adjustment only; clean the oil from the slide and 100× objective after use.

Which adjustment knob should you use when focusing with the 100× oil-immersion objective? Fine adjustment only. Do NOT use the coarse adjustment.

Why is it important to clean the oil-immersion lens after using it? Oil left on the objective can interfere with future observations and can damage or contaminate the lens if it is not properly cleaned.

What is the difference between magnification and resolution? Magnification makes the specimen appear larger, while resolution allows you to see two close objects as separate and distinguish fine details.

Which objective lenses can generally be used with the coarse adjustment knob? The 4× and 10× objectives. Use the fine adjustment with higher-power objectives.

Why does oil immersion improve the image? The oil reduces light refraction between the slide and objective, allowing more light into the objective and improving resolution.

If a microscope is parfocal, what should happen when you switch from 10× to 40×? The specimen should remain mostly in focus, although you may need a small adjustment with the fine-focus knob.