Review of the Microscope

Who Invented the Microscope?

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- Some scientists have credited Zacharias Janssen of the Netherlands for inventing the optical microscope in the early 1600’s.

- Anton van Leeuwenhoek, a Dutch biologist, has gotten more of the glory since his 18th century single-lens microscopes worked better and were more widely used. He was also the first to discover bacteria and protozoans.

From www.howstuffworks.com (History of the Microscope)

(Ocular)

Diaphragm

Microscope Parts & Functions

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FUNCTION: PART:

The lens you look through, magnifies the specimen. Ocular Lens

Supports the microscope. Base

Holds objective lenses. Revolving nosepiece

Magnify the specimen. Objective lenses

Supports upper parts of the microscope, used to carry the microscope.

Arm

Used to focus when using the high power objective. Fine focus

Where the slide is placed. Stage

Controls the amount of light reaching the objective lens.

Diaphragm

Used to focus when using the low power objective. Coarse focus

Provides light. Illuminator

Hold slide in place on the stage. Stage Clips

Biological Drawing Rules

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Drawing is neat and LARGE. Must take up most of the paper

Diagram is drawn in pencil and “coloured” using stipples (little dots)

All diagram labels are printed to the right of the drawing and are lined up in a straight line

Name and date are written in the upper right hand corner of the diagram

An appropriate title is given to the diagram

Lines between label and feature are drawn using a ruler

Lines do not cross

Calculations and qualitative observations are included at the bottom of the diagram

Amoeba

Mr. KassSeptember 9, 2011

Endoplasmic reticulum

Mitochondria

Nucleus

Vacuole

M = ocular x objective M = (10X) x (40X)M = 400X

- Specimen was transparent.- Nucleus appeared to be a pink/purple colour

1) Magnification (M)

• Definition: how many times bigger an image appears to the eye

• Formula: M = ocular lens x objective lens

• Ocular Power (eye piece)

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Example

• A student uses high power (40X) to look at a cell. The ocular lens has a power of 10X. What is the total magnification she is using?

• M = ocular lens x objective lens

• M = (10X) x (40X)

• M = 400X

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2) Field of View (FV)

• Definition: the diameter of the circle you see when you look down a microscope. (how much you can see)

Field of View (FV)

Low FV = measured with a ruler (in mm) on low power

• Use formulas for medium and high power:

Medium FV = FVLOW X (MLOW/MMEDIUM)

High FV = FVLOW X (MLOW/MHIGH)

• Where “M” stands for magnification

• Why can’t we use a ruler to measure FV for medium and high power?

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3) Specimen Size (SS)

• Definition: the actual size of the object you are looking at (measure the greatest length you can find)

• Formula: SS = FV / # of specimens that will fit across your FV

• Example: The field of view in the diagram below is 27μm. What is the approximate size of the amoeba? SS = 27 μm / 3

SS = 9 μm

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4) Diagram Magnification (DM)

• Definition: how many times bigger your diagram (drawing) is compared to the actual specimen

• Formula: DM = size of drawing (mm) / SS (in mm)

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Skill 1: The MicroscopeIn-Class Assignment

• Work in pairs, hand in an individual assignment

• For the paramecium OR animal cell slide, locate the specimen on your microscope and sketch a biological diagram

• Use the biological diagram rules we discussed earlier as a checklist/rubric

• Use the formulas you learned to calculate the actual size of the specimen

• Will be marked out of 10 for communication

Key areas to remember:

• Quality of the diagram counts

• Correctness of calculations

• Label any 3 cell parts (use the checklist/exemplar)

• Sophistication of observations