The Microscope
Types of Microscopes
The Compound Light Microscope
 Two lenses (objective and ocular)
 Specimen is illuminated from an electric lamp or external light source
 Has both magnification and resolution
The Transmission Electron Microscope (TEM)
 An invisible beam of electrons travel through the specimen
 The specimen must be cut and put onto a fine metal grid containing
holes so that electrons can pass through it
The Scanning Electron Microscope (SEM)
 Electrons are reflected from the surface of the specimen
 It uses magnets to focus the beam
 It cannot magnify or resolve as well but the specimens are alive
Label the Microscope
Label the Microscope
Low power
objective
Medium power objective
High power objective
Microscope Parts
 Base: stable platform for microscope
 Light Source: provides light to the
slide
 Diaphragm: controls the amount of
light given to slide
 Stage: supports the slide, allows light
to enter
 Stage Clips: hold the slide in position
Microscope Parts
 Arm: used to carry microscope, holds
tube in place
 Body Tube: contains the eyepiece
(ocular lens) and supports the
objective lenses
 Revolving Nosepiece: holds the
objective lenses and rotates them
 Ocular Lens (eyepiece): What you
look through, magnifies object
Microscope Parts
 Objective Lenses: Magnify with low,
medium, and high power
 Coarse Adjustment Knob: Moves body
tube up or down to focus object. Use
ONLY with low power!
 Fine Adjustment Knob: Moves the tube
to sharpen an image. Use ONLY after
focused with coarse adjustment knob
Scientific Drawings
Scientific drawings are done to show and describe things
that contain a lot of detail.
Rules for creating scientific drawings:
 Use a blank sheet of paper
 Use a sharp pencil (NO pen!)
 Use at least half a page for each drawing (make it large
enough to show the details)
 Draw closer to the left hand side of the page – leave the right
hand side for labels (labels should line up on right hand side)
 Using a ruler, label important parts of the object
 Title your drawing (include magnification beside the title, both
underlined)
 Draw ONLY what YOU see!
 Do NOT sketch
 Do NOT use shading or colouring, instead use stippling (dots).
Scale ratio
To calculate the scale ratio:
 Scale ratio =
𝒔𝒊𝒛𝒆 𝒐𝒇 𝒅𝒓𝒂𝒘𝒊𝒏𝒈
𝒂𝒄𝒕𝒖𝒂𝒍 𝒔𝒊𝒛𝒆 𝒐𝒇 𝒐𝒃𝒋𝒆𝒄𝒕
 *The magnification is always written
with an “X” after it at the bottom right
hand corner, followed by the actual
size and then the scale ratio.*
Calculating Magnification
 Each objective lens has its own magnification
 Low Power = 4x
 Medium Power = 10x
 High Power = 40x
 The ocular lens also has a magnification of 10x
TOTAL MAGNIFICATION = ocular lens x objective lens
 Ex: Viewing a specimen under low power
magnification:
Total magnification = 10 x 4
= 40x
Field of View
 The circular area that you see when you look
through the ocular lens
 It is important to know the diameter of your
field of view so that you can get an idea of
the size of the specimen
 Measured in mm
Field of view diameters:
 Low power: 4.5 mm
 Medium power: 1.8 mm
 High Power 0.4 mm
Estimating Cell Size
 Estimated Cell Size =
𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝐹.𝑂.𝑉.(𝑚𝑚)
𝐴𝑝𝑝𝑟𝑜𝑥.# 𝑜𝑓 𝑜𝑏𝑗𝑒𝑐𝑡𝑠 𝑎𝑐𝑟𝑜𝑠𝑠 𝐹.𝑂.𝑉.(𝑚𝑚)
Ex: Estimate the cell size for the skin cell viewed
under low magnification
Cell size =
4.5 𝑚𝑚
5
= 0.9 mm