MICROSCOPE PRACTICE LAB

Objectives:

1. To identify and label items under microscope.

2. To estimate the size of a microscope field of view and its specimens.

3. To increase your powers of observation and your attention to detail.

PART ONE: Estimating the size of an object under a microscope

One of the first things an observer of cells must do is to be able to estimate the size of their cell with a 90% accuracy. It is far easier than it seems. Follow these instructions, step by step, and soon you will become skilled at estimating the size of any sample you observe under the microscope.

Step 1

Determining your magnification.

List the total magnifications of your microscope.

dissect power ______low power ______high power ______

REDYELLOWBLUE

Step 2

Determining your field of view.

From your instructor, get a protractor that measures millimeters. Place your ruler under your scope and focus at 100x. Place your ruler so that the beginning of one line is at the far left side ( see illustration below). Your field of view is the diameter, from left to right, of your microscope. One millimeter is equal to 1000 microns (1000  Measure the diameter of your field of view.

Determine the FOV for all magnifications of your scope.

field of view (FOV) at dissect low power _____

*field of view (FOV) at low power (yellow) _____

*field of view (FOV) at high power (blue) _____

Step 3

Estimating the size of your specimen.

Once you have determined the FOV, estimating the size of your organism is easy. Determine the length of your organism compared to the diameter of your microscope. For example, If two of your organisms could fit end to end across the diameter of your FOV, it is about half the size of your diameter. Simply multiply your FOV by 1/2. This formula will hold true for any magnification.

Formula for calculating organism size

organism = FOV * (1/# of organisms end to end across the diameter)

Step 4 microscope observations

Diagram your samples. * Microscope drawing rules apply *

Directions: Observe each specimen in the list below. Each partner should estimate the size of the specimen and then compare answers. Remember, your estimates must have a 90% accuracy. Carefully diagram your specimen (microscope drawing rules apply). Take the time to observe for detail. Your score will be weighed heavily upon your dedication to detail. You may use this sheet and may add other sheets of paper as needed. * Reminder, This is your lab, find a way to complete it on your own.*

Observation List (you can observe these in any order)

  1. wetmount small case letter “e” 1 sketch on L.P.
  2. dry mount salt crystal: 1 sketch on L.P. (label cracks, salt crystal)

Step 4 microscope observations

Diagram your samples. * Microscope drawing rules apply *

Directions: Observe each specimen in the list below. Each partner should estimate the size of the specimen and then compare answers. Remember, your estimates must have a 90% accuracy. Carefully diagram your specimen (microscope drawing rules apply). Take the time to observe for detail. Your score will be weighed heavily upon your dedication to detail. You may use this sheet and may add other sheets of paper as needed. * Reminder, This is your lab, find a way to complete it on your own.*

Observation List (you can observe these in any order)

  1. wetmount small case letter “e” 1 sketch on L.P.
  2. dry mount salt crystal: 1 sketch on L.P. (label cracks, salt crystal)

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