MICROSCOPE

Parts of the Microscope

a. Eyepieceb. Coarse Adjustmentc. Fine Adjustmentd. Objectives (LP, HP)e. Armf. Stageg. Light sourceh. Basei. Diaphragm

FUNCTIONS – FILL IN AT BOTTOM

OF SHEETa. Magnifies image (10X)b. Used for rough focus (use with

low power)c. Used for fine adjustments (use

with high power)d. Enlarges image (scanning 4x, low

power 10x, high power 40x)e. Used for carrying microscopef. Platform for holding the slideg. Can be a mirror or light bulbh. Used for carrying the microscopei. Adjusts the amount of light

B. The compound light microscope can be used to view specimens that have dimensions of less than 0.1 millimeter. You can calculate the total magnification of a specimen by multiplying the magnification of the eyepiece lens by the magnification of the objective lens.

• 10x x 4x = 40x magnification magnification total of eyepiece lens of obj. lens

magnification

The specimen being viewed is magnified 40 times. The

greater the total magnification, the smaller the field of view

(FOV) or area that you see. The lower the total magnification,

the larger the field of view (FOV).

Question 1:

• Calculate the total magnification:Eyepiece

LensObjective

LensTotal

Magnification

a. 10x 4x 40xb. 10x 10x 100xc. 10x 40x 400x

Questions 2 & 3:Question 2:

• With which combination of lenses would you be able to see the largest area of a specimen? Eyepiece & scanning(4x) (largest FOV) or eye & low power ( 10x) if scanning is not there

• The smallest area? Eyepiece 10x & High power 40x (smallest FOV)

Question 3:

• Which set of lenses would you use to locate a specimen on a slide? Eye & 4x(scanning) or 10x (low power)

• Which set would you use to examine the details of a specimen? Eyepiece & 40x (high power)

HIGH POWER

FIELD OF VIEW

-How much can you see? In High Power we see 25% of the low power FOV (low power 100 x is 25% of high power 400x) We see less of the specimen but we see more details of the specimen under high power

LOW POWER

Answer the following Questions • 1. After switching from high power to low power the area of

the field of view will appear• a. larger and brighter• b. Smaller and brighter• c. larger and darker• d. smaller and darker• 2. What should a student adjust if the field of view seems too

dark?• ________________________________• 3. Is the field of vision smaller or larger under low • power? ______________________________________

• 4. To locate and observe a specimen under a slide, a student should begin by using what objective and what adjustment knob?

• 5. What adjustment knob should you use if you are using high power?

• 6. Why should a specimen be centered in the middle of the field of view when focusing under low power?

Electron Microscope

The limit of resolution restricts the usefulness of light microscopes for studying VERY small specimens such asviruses.• Electron microscopes use a stream of electrons to view these specimens.• Electron microscopes have a limit of resolution more than 1000 times finer than light microscopes.

http://www.answers.com/topic/misc-pollen-jpg

FIELD OF VIEW

How do we find the FOV of a microscope?

Low Power (100x)1.Find the diameter of the LP FOV2.Use the clear metric ruler (mm side)3.Be sure to line up the first mm mark with the left side of the field.

LP FOV = 1.5 mm

The mm is too large to measure

microscopic objects, so you need to use the

micron (micrometer)

µm

• 1 mm = 1,000 µm• 1 µm = 1/1000 mm or 0.001mm

LP FOV = 1500µm

So how do we determine how big something is in the microscope?

• Let’s see how it works:

Use the following formula:

FOV# of cells

(that can fit across

diameter)

FOV = 2mm = .5mm # of 4cellsOR .5mm x 1000 =500 microns