Microscope - Exercise 1

Objectives-Familiarize parts and functions of the microscope.-Calculate total magnifications.-Determining the Diameter of the field of view for different magnifications.-Estimate size of an object under the microscope.-Identify parts (organelles) in animal and plant cells.

Condenser: It will gather the light from the illuminator and focus it on the specimen lying on the stage. The function of the

condenser is to focus the light rays from the light source onto the specimen.

Iris diaphragm lever: This allows the amount of light passing through the condenser to be regulated to see the object.

Microscope

You have to learn how to use the microscope

if your going to take Anatomy & Physiology,

BI203, or any other science related courses, so

get a good hang out of it now. Also, learn the

parts and functions of the microscope.

Measuring Objects with the Microscope

-To focus on an object, you must first center the object

to the center of the field of view, and remember to do this

every time you switch to a higher magnification.

-The field of view refers to the total area that is visible through

the microscope. The field of view is circular. The field gets

smaller as the magnification increases. It is possible to

measure the diameter of the field of view, and that

measurement can then be used to construct reasonable estimates

of the size of any specimen contained within the field of view.

Measuring Objects with the Microscope

With the 4x objective lens in place, look through the microscope and adjust the ruler so that it lies

on a diameter of the field of view.

Calculating the Diameter of the Field of View at other Magnifications

There is an inverse relationship between the total magnification and the diameter of the field of view – i.e., as magnifications increases the diameter of the field decreases in proportion, so the diameter of field of view at different magnification can be calculated mathematically, using the formula.

Known magnification

----------------------------- X original um = Diameter of

Unknown magnification Field of View

Page 11 – Lab Book

Dimensional Analysis

• You are converting um (10-6 m) mm (10-3 m)

• 1um 10-6 m 10-6

• 1 mm 10-3 m - 10-3

= 10-3

1um x 10-6 m x 1 mm = 10-3 aka 1,000 um/mm1 um 10-3m

• Diameter of the field of view at 40x (low power) which is objective lens 4. To convert the diameter of field to micrometer you just multiply it by 1,000, and you could get whatever you measured your ruler. So lets say we measured our ruler to be 4mm, so we multiply it by 1,000, and we get 4,000 um. Now, we could get other diameter of fields with different magnifications using a formula.

• For example, say we have to find the diameter of field of 100x?

• The first thing you do is put 40, which is your total magnification that you started with, over your unknown magnification, then you multiply that by your total micrometers, so for this case its 4,000, and you get a diameter of field of 1600 um.

• Now, say their asking us for 430x magnification, so what we do is put 40 over 430, and you multiply that by 4,000 which you would get 372 um.

• Determining the Diameter of the field of view at 40x (low power) (Ruler)

• With the 4x objective lens (40 magnification) in place, look through the microscope and adjust the ruler so that it lies on a diameter of the field of view.

Estimate size of an object under the microscope

The approach you would take to estimate the size of amicroscopic object, if you are given the diameter of field ofviews at different magnifications.

• Step 1: Focus on the object at certain magnification and note the diameter of the field of view at that magnification.

• Step 2: Determine (guesstimate) the percent of the diameter of the field of view is occupied by the object (image).

• Step 3: Use the following formula…..

PercentObject Size = ------------------ X diameter of field of view =

100

Estimate size of an object under the microscope

The size of a specimen can be estimated by comparing it to the knowndiameter of the field of view at any magnification. First, you have to estimatehow much of an object is occupying the field of view of the microscope, soyour not going to get an accurate answer, but your answer should get ananswer that’s going to be within a range.

Ok, your still using the 4,000 um that you get previously and say youhave a flea, and that flea takes up about 40% of your microscope, sowhat you do is covert the 40% into a decimal by dividing it by 100, andyou get .40 then you multiply that by 4,000 um and you should get ananswer, which is 1600 um.

Now, they can ask you to estimate another size of an object. Forexample, say the Flea’s eye covers about 5%. So you divide that 100,you should get .05 and multiply that by 4,000 um, and you should get 200 um.

Note: You could be asked this at different magnifications.

Your going to be ask to

identify parts of both animal

and plant cells, such as

chloroplast, nucleus of a cell,

and those sorts of things, so

review them on your own.

Human epithelial cell – From Rust – 1a & 1b

• You will need to identify the nucleus, cytoplasm, and the cell membrane under a microscope.

Elodea Leaf cell – From Rust – 1c & 1d

• You will need to identify the cytoplasm, cell wall, and chloroplast under a microscope.

What is the function of the chloroplasts?

What is the function of the chloroplasts?

Photosynthesis to make food for the plant.

Calculate the diameter of the field of view occupied by the flea. The diameter field of view is 100x magnification of the microscope is 380 micrometer. You have to estimate the percentage of the flea that occupies the microscope. This is subjective.

Questions1. In the diameter of field of view of a light microscope at

40X magnification is 6,000 micrometer (um), what would be the field of view at 400X magnification?

2. An elodea cell was found occupying 40% of field of view’s diameter at 400X magnification. At this magnification the field of view of the microscope is 200 micrometer. What is the size of the elodea cell? Remember this is a gesstimate percent of the diameter of the field of view is occupied by the object (image).

Questions1. In the diameter of field of view of a light microscope at 40X magnification is

6,000 micrometer (um), what would be the field of view at 400X magnification?

40 x 6000 = 600 um400

2. An elodea cell was found occupying 40% of field of view’s diameter at 400X magnification. At this magnification the field of view of the microscope is 200 micrometer. What is the size of the elodea cell? Remember this is a gesstimate percent of the diameter of the field of view is occupied by the object (image).

40 = .4100

.4 x 200 = 80 um