lab #3 3-1 pt 2

Centering the specimen

What should you do before switching to a higher-power objective? You should center the desired portion of the specimen in the field of view.

Importance of centering

Why should the specimen be centered before increasing magnification? The field of view becomes smaller, so an off-center specimen can easily be lost at higher magnification.

Image view of the letter 'e'

What happens to the image of the letter 'e' when viewed through a compound microscope? The image appears inverted/reversed compared with the original.

Movement of stage toward you

If the microscope stage is moved toward you, which direction does the image appear to move? The image appears to move away from you.

Movement of stage to the right

If the microscope stage is moved to the right, which direction does the image appear to move? The image appears to move to the left.

Letter 'e' exercise demonstration

What does the letter 'e' exercise demonstrate? The image viewed through a compound microscope is inverted relative to the specimen.

Colored-threads exercise purpose

What is the colored-threads exercise designed to demonstrate? That specimens can contain structures at different depths, requiring careful focusing to determine their order.

Focus adjustment for colored threads

Which focus adjustment is especially important for determining the order of the colored threads? The fine-focus adjustment.

Effect of closing the iris diaphragm

Why can closing the iris diaphragm help when viewing the colored threads? It can improve contrast, making differences between structures at different depths easier to see.

Colored-threads exercise significance

What does the colored-threads exercise demonstrate about specimens you'll observe later? Specimens may have structures located at different focal planes, so careful focusing is important.

Dark-field microscopy

What is dark-field microscopy? A type of microscopy in which a special condenser allows primarily light reflected from the specimen to enter the objective, producing a bright specimen against a dark background.

Phase-contrast microscopy

What is phase-contrast microscopy? A technique that uses differences in the refractive indices of water and cellular components to produce contrast.

Usefulness of dark-field or phase-contrast microscopy

Why can dark-field or phase-contrast microscopy be useful? They can provide contrast for specimens that are difficult to see with ordinary bright-field microscopy without staining.

Bright-field microscopy in microbiology

Why is bright-field microscopy especially useful in introductory microbiology? It is the most commonly used light-microscopy method in introductory classes and clinical laboratories.

Basic path of light through a compound microscope

What is the basic path of light through a compound light microscope? Light source → condenser → specimen → objective → ocular → eye.

Microscope performance evaluation concepts

What are the three main concepts to remember when evaluating microscope performance? Magnification, resolution, and contrast.

Field of view and magnification

What happens to the field of view as magnification increases? It decreases.

Specimen detail and magnification

What happens to the amount of specimen detail visible as magnification increases, assuming adequate resolution? More detail becomes visible.

Cleaning microscope lenses

What should you use to clean microscope lenses? Lens paper or the appropriate microscope-cleaning material; avoid excessive pressure because lenses can be scratched.

Oil-immersion objective rule

What is the most important rule when using the oil-immersion objective? Only use oil with the objective specifically designed for oil immersion.