Lab 4: Microscopy

Magnification

An increase in the apparent size of an object

the fine adjustment knob is used to

fine tune the focus

the microscope has ____ objective lenses to magnify the image

four (4x, 10x, 40x, 100x)

Using an oil immersion objective lens allows for

higher magnification

what is important to remember when using oil immersion?

immersion oil can only be used with the 100x objective, and without it the image is blurry

field of view

is the amount of the slide you are able to see through the eyepiece

total magnification

is the overall enlargement of the image of a species objective lens x ocular lens(10x)

the coarse focus ring is used to

locate the focus plane

three factors that determine the quality of a microscopic image:

magnification, resolution, contrast

one method to prepare a sample for viewing under the microscope is to

make a wet mount

the oil ____ be removed before using the other objective lenses

must

the stage adjustment knobs are used to

navigate in the sample (upper knob moves back and forth, lower knob moves side to side)

a single drop of pond water may contain

numerous types of bacteria, algae, protozoa, rotifiers, hydra, and many more

contrast

refers to the ability to distinguish objects such as cells from the background

when focusing on a slide start with...

scanning/ low power objective lense. the lower power lens has the greater field of view

without immersion oil

some of the peripheral light that passes through the specimen is scattered into air or the slide, decreasing resoultion

to move the slide you move the

stage (the stage knob on the top moves the stage forward and back, the stage knob on the bottom moves the stage side to side)

cytology

study of cells

pathology

study of disease

Histology

study of tissues

what is the advantage of starting with the 4x objective before moving to the 10x and then the 40x objective?

the field of view is larger and its easier to focus

How do the coarse and fine focus knobs work on a brightfield microscope?

the focus knobs move the stage up and down

Why should the fine focus knob typically be used with the 10X and 40X objective lenses?

the slide should be close to in focus after focusing at the 4x objective. focusing with the coarse focus knob would result in too large a change in focus.

what are the advantages to using a wet mount slide preperation?

the specimen may be alive, the specimen could be viewed moving, the specimen behavior can be viewed

the goal of microscopy is

to create a magnified image of objects too small to be seen with the eye alone

oil immersion is

when a drop of immersion oil is added to the slide, contacting both the sample and objective

to adjust the lighting in the microscope

- as magnification of the image increases, the light intensity decreases and will have to adjusted - the condenser lens focuses the light on the slide -the sliding bar on the condenser lens is the aperture. as you move the aperture to decrease the light to the slide the contrast increases. as you move the aperture to increase the light o the slide, the contrast decreases

the advantages of wet mount may include:

-Fast preparation. -Requires no special equipment other than a transfer pipette, slide, and cover slip. -Organisms may be viewed in their living state. -Movement of motile microorganisms can be observed.

correct order of steps to view a specimen at 40x magnification

1. click power switch to turn on light 2. adjust light to appropriate brightness 3. focus at 4x using coarse focus knob 4. adjust ocular lenses to view one image 5. focus using fine focus knob 6. adjust the stage to move the star to the center of the microscope view 7. put 10x objective in place 8. focus using fine focus knob 9. put 40x objective in place 10. adjust using fine focus knob

steps to use immersion oil

1. focus on the cell in the slide with the yellow star using 4x objective. use coarse and fine focus knobs to focus 2. rotate nosepiece to 10x. focus using fine focus knob 3. rotate to 40x. focus using fine focus 4. rotate halfway to 100x. apply one drop of immersion oil to slide 5. rotate 100x lens into oil drop. use fine focus knob to focus 6. rotate nosepiece to blank space next to 4x objective. using lens paper, remove immersion oil from 100x objective and slide.

steps for changing objective lenses

1. rotate nosepiece to 4x objective' 2. focus using coarse focus knob 3. once your image is in focus, use fine adjustment knob to sharpen 4. rotate nosepiece to 10x and focus using fine focus 5. rotate to 40 x and focus using fine focus knob

steps to create a wet mount

1. using pipette, obtain a drop of pond water and place in center of slide 2. using tweezers, add cover slip. be careful to avoid air bubbles trapped between the slide and cover slip 3. place slide onto microscope stage 4. use fine focus knob to adjust image.

What is the total magnification of a specimen using the 40x objective?

400x

Microbiology

A branch of biology dealing especially with microscopic forms of life (as bacteria, protozoans, viruses, and fungi).

ocular lens

Eyepiece of a microscope can be adjusted to fit your eyes

brightfield microscopes use

a combination of glass lenses and light to view the specimen

Resolution

ability to distinguish fine detail

focus is achieved by

adjusting the distance between the specimen and the objective lens (focus knob controls the up and down movement of stage)

microscopes are often used to study

bacteria, cells, tissues

higher magnification is achieved by

changing the objective lens

which of the three factors affecting image quality is altered by light source?

contrast

Fields of study where a microscope is a necessary tool include:

cytology, histology, pathology, microbiology