MICROSCOPES

• The microscope is an instrument that allows us to see objects that are normally too small for the eye to see

•It was invented by Anton VanLeewenhoek in the 1600’s

•Robert Hooke was the 1st to see cells

Types of Microscopes

1. Simple Microscope – a single lens (eg. magnifying glass)

2. Compound Light Microscope – light is projected through 2 lenses to view an “image” of an object. The image is somewhat blurry.

BEST FOR VIEWING LIVE SPECIMENS

pg. 16 – Human Cheek Cells - cell organelles stained green and nuclei yellowpg. 29 – Egg Cell – surrounded by smaller cells that support and nourish egg

3. Electron Microscope – uses a beam of electrons to take a magnified ‘picture’ of an object.

eg. T.E.M. – Transmission Electron Microscope• designed by James Hillier• to view specimen, it is encased in plastic and shaved into very thin layers, allowing electrons to pass through it, therefore can only be used to view dead cells

pg. 19 – goblet cellpg. 37 - lysosome

eg. S.E.M. – Scanning Electron Microscope• reflects electrons from the surface of the specimen, allowing thicker specimens to be used

The electron microscope can magnify objects to a very large size. The picture of the object is very clear.

pg. 21 – RBCpg. 27 – Sperm Cellspg. 148 -RBC & capillary

Important Vocabulary

Magnification – apparent enlargement of an object - a magnification of 100X means that the object is 100 times bigger than the actual object

Resolution – clarity, sharpness - the ability of a microscope to show two very close points

Electron Microscope Compound Microscope

Approximate Size Several m3 Compact

Cost $ 10 6 Max. $3000

Magnification‘enlargement of an

object’

> 10 6 400 – 1000 max.

Resolution‘clarity, sharpness’

Very high Limited by wavelength of light

Training 2 years (tech) 1 class

Illumination Electron beam Light

Characteristics of a Compound Light Microscope

1. When you go from low to medium to high power the:•light gets dimmer• field of view gets smaller• image gets bigger

2. The ‘image’ of an object under the microscope appears “backwards”

For our school microscopes to calculate total magnification:Total Mag : objective power x ocular lens (10X)

Low Mag : 4 X 10 = 40XMed Mag: 10 X 10 = 100XHigh Mag: 40 X 10 = 400X

The Diameter of the Field of View

MagnificationOcular Objective

Specimen Magnification Field of View Diameter(mm) (um) diagram

10X 4X (low)

10X (med)

10X (high)

Converting mm --- µm Sample Calculation: 4 mm =

1 mm = µm1 mm = µm

Activity1. Estimation of Specimen Size – handout

2. Using prepared slides, Letter e, HYDRA and Volvox, sketch and estimate actual size

Diagram- diagram is done in pencil- sketch (stipple) diagram on left side of blank paper & labels on right- diagram needs a title- include total magnification