MICROSCOPE

Parts of the Microscope Eyepiece Coarse Adjustment Fine Adjustment Objectives (LP, HP) Arm Stage Light source Base Diaphragm

FUNCTIONS – Magnifies image (10X) Used for rough focus (use with low power) Used for fine adjustments (use with high power) Enlarges image (scanning 4x, low power 10x, high power 40x) Used for carrying microscope Platform for holding the slide Can be a mirror or light bulb Used for carrying the microscope Adjusts the amount of light

To Find Total Magnification How large is the cell in the diagram below? Multiply the eyepiece and the objective lens to get the total magnification. 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).

Calculate the total magnification Eyepiece Lens Objective Total Magnification a. 10x 4x 40x b. 10x 10x 100x c. 10x 400x

REVIEW QUESTIONS 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) 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 LOW POWER -How much can you see? 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 HIGH POWER

More Review 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? ______________________________________

Even more review questions: 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 as viruses. • 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.

FIELD OF VIEW Low Power (100x) Find the diameter of the LP FOV How do we find the FOV of a microscope? Low Power (100x) Find the diameter of the LP FOV Use the clear metric ruler (mm side) Be sure to line up the first mm mark with the left side of the field. LP FOV = 1.5 mm

1 mm = 1,000 µm 1 µm = 1/1000 mm or 0.001mm The mm is too large to measure microscopic objects, so you need to use the micron (micrometer) µm LP FOV = 1500µm

So how do we determine how big something is in the microscope? Let’s see how it works: So how do we determine how big something is in the microscope? Use the following formula: FOV # of cells (that can fit across diameter) FOV = 2mm = .5mm # of 4 cells OR .5mm x 1000 =500 microns