BIOL 1615 - exercise 3, The Microscope, quiz review

What are the three basic functions of a microscope?

1. Magnify object - image appears larger 2. Improve a resolution - ability to distinguish two points as separate. 3. Contrast - Difference between lightest and darkest areas.

Basics for using microscope

1. always start and end on the lowest power objective 2. use the coarse adjustment only on the lowest power objective. use the fine adjustment for all other objectives. 3. center and focus specimen on lowest power objective before moving to higher objective. 4. never force an objective into place as you're moving to higher objectives. 5. Only lens paper for cleaning lenses.

When you are finished using your microscope, which of the following should you never do: a. clean lenses with kimwipe or paper towel b. wrap electric cord securely around arm c. return microscope to designated area d. clean lenses with lens paper

A - clean lenses with kimwipe or paper towel

Lens paper

A delicate sed for cleaning

Wet Mount

A slide prepared by adding a drop of liquid (such as pond water or an algae culture) and gently lowering a clean coverslip on top at an angle.

Keeping lab safety in mind, why should you not put broken glass in the trash can?

Broken glass should not be put in the trash can because it poses a safety cut hazard. It needs to be disposed of in a secure manner to prevent contact.

From the previous quesion, what is your total magnification? a. 1 b. 10 c. 100 d. 1000

C 100 = 10x10

When preparing a wet mount, how do you eliminate air bubbles? a. drop coverslip directly onto sample b. do not use water c. starting at a 45* angle, slowly lower coverslip onto sample d. none of the above

C - Starting at a 45* angle, slowly lower coverslip onto sample

When carrying your microscope... a. tuck it under one arm like a football b. carry it with both hands under the base c. carry it with one hand holding the arm and the other supporting the base d. Carry it with both hands on the arm

C - carry it with one hand holding the arm and the other supporting the base.

How much more area is there in the 10x objective compared to the 100x objective? a. 10 b. 0.1 c. 100 d. 0.01

C- 100

If your occular lens has a magnification of 10x and you have your microscope set on the 10x objective, how would you calculate your total magnification? a. ocular magnification / objective magnification b. (ocular magnification)2 c. (objective magnification)2 / ocular magnification d. ocular magnification x objective magnification

D Mag tot = Mag 0cu x Mag Obj or total = 10 x (4 or 10 or 40)

Why is depth of field important in studying biological structures? How can it affect your ability to find and examine a specimen?

Depth of field is important in studying biological structures because it varies with different objectives and magnifications as well as allows you to examine the specimen in 3-D structure. It can affect your ability to find and examine a specimen because the higher the magnification, the field of view gets smaller. This can make viewing the specimen difficult because some parts will be focused and other parts blurry.

When focusing on high power... a. only use the coarse adjustment b. only use the fine adjustment c. never use the coarse adjustment d. never use the fine adjustment e. both b and c

E - only use the fine adjustment and never use the coarse adjustment.

Stage clips

Holds the slide in place

Magnify

Increases the specimens apparent size

What is the importance of adjusting the light intensity when viewing specimens with a compound microscope?

It is important to adjust the light intensity when viewing specimens because too much light or too little light might make it hard to view the specimen. You need to adjust the light intensity to make the specimen more visible and clearer.

What are the advantages of knowing the diameter of the field of view at a given magnification?

Knowing the size of the field of view is important because you can use it to estimate the size of an object you are examining.

The Mag (ocu) on our Microscopes is always 10x. If you are using the 10x objective lens, what is your total magnification?

Mag (tot) = 10x10=100

Calculating Magnification

Mag (tot) = Mag (obj) x Mag (ocu)

Calculate FOV

Measure the FOV on low power (4x). Use the diameter to calculate the radius lastly, plug the radius into your formula for area of a circle A=πr2 Using the formula for area of a circle, you can calculate how much more area one magnification has compared to another. Considering that the magnification of the 10x objective is 2.5x greater than the 4x objective. It can be concluded that the FOV diameter of the 4x objective is 2.5x larger than the 10x objective. Using A=πr2 we can conclude that the area of the 4x is 2.5square or 6.25x larger than the 10x.

coarse focus knob

Moves the stage up and down quickly. Used to find a specimen when using the low power objective.

Why must specimens viewed with a compound microscope be thin? Why are they sometimes stained with dyes?

Specimens viewed with a compound microscope must be thin so light can pass through them. Sometimes specimens are stained with dyes to help increase contrast and make the specimen more visible.

Resolution

The ability to distinguish two points as separate points.

Contrast

The amount of difference between the lightest and darkest parts of an image.

Illumination

The amount of light required to see your specimen clearly (more is required at higher powers).

What is the appropriate material for cleaning the lenses of a microscope? Why do you think only this should be used?

The appropriate material for cleaning the lenses of a microscope is lens paper. If lens paper is not used, the lenses of a microscope could get scratched.

Field of View

The area visible when looking through the ocular and objective (FOV decreases as magnification increases).

At which magnifications should the course focus adjustment be used?

The coarse focus adjustment should only be used when you are viewing a specimen with the 4x or 10x objective lens.

What is the difference between magnification and resolution?

The difference between magnification and resolution is that magnification increases the specimen's apparent size whereas the resolution is the ability to distinguish two points as separate points (gives an image higher or better resolution to help make an image sharper).

Depth of field

The thickness of the object in sharp focus (Depth of Field decreases as magnification increases).

Examine the micrograph of the letter e shown in figure 3.4. This letter is magnified 40X. What is the actual height of the letter?

To determine the actual height of the letter "e", take your measured FOV diameter (5 mm) and estimate how much of that the letter "e" takes up (~75%) 5 mm x 0.75 = 3.75 mm

T/F A low power objective will give you greater depth of field than a high power objective

True

T/F A low power objective will give you a greater FOV than a high power objective.

True

fine focus adjustment

a knob that makes small adjustments to the focus (it is often smaller than the coarse focus knob).

stage

a platform that supports a slide holding the specimen

Match the following terms with their definitions: 1. magnification 2. resolution 3. illumination 4. contrast

a. more is required at higher power magnification b. ability to distinguish two points as separate c. can be improved with a stain d. ability to increase apparent size 1)d 2)b 3)a 4) c

Iris diaphragm

adjusts the amount of light that reaches the specimen Stage: the flat platform where the slide is placed

Coarse adjustment

brings specimen into focus

Fine adjustment

fine tunes the focus and increases detail of specimen

Condenser

gathers and focuses light from light source to specimen being viewed

par focal - fine focus

lens that stays in focus when magnification/focal length is changed

Oculars

lens that you look through

Objective lenses

lenses that are closest to specimen

condenser iris diaphragm

regulates the amount of light reaching the specimen

par centered - fine focus

stays centered when increasing magnification.

condenser adjustment knob

used to obtain best illumination by raising or lowering condenser

When you examine a specimen with a compound light microscope, why should you start focusing using the low and not the high-power objective?

you should always begin focusing using the low (scanning objective) because it enables you to scan large areas of a specimen. You don't want to start with the high-power objective because you will only be able to scan small areas of a specimen.