Microscopes

The Discovery of Cells

Quiz

Number paper from 1-5

Identify the following pictures

Question 1

Question 1: Bacteria

Question 2

Question 2: DNA

Question 3

Question 3: Breast Cancer Cell

Question 4

Question 4: Alga- red tides

Question 5

Question 5: Bed bug

Learning Targets

1. Describe how a microscope works.

2. Calculate the total magnification of an image.

3. Compare the different types of microscopes.

Why? To see microscopic world

How does a microscope work?

Magnificationenlargement of an objectcompare size of image to actual size of

object

total magnificationocular power x objective power = total

magnification

Microscopes

MicroscopesResolution – capacity to show 2 points that are close together as separate

. . .

10x 1000x

Poor Resolution = Blurry ImageGood Resolution = Clear Image

Resolution

How does a microscope work?

Parfocalboth low and high power objectives are

adjusted to the same focuseasily switch between both objectives

What happens as magnification increases?

1. field of view decreases

2. brightness decreases

3. resolving power increases

Staining

Coloring cell structure

With dyes to reflect light

Certain cell parts absorb certain stains

Kills cells or disturbs contents Vital stains-dyes that highlight structures

in living cells

What are the different types of microscopes?

Compound light microscope

Stereoscopic dissecting microscope

Electron microscope

Compound Light Microscope

Compound Light Microscope

has 2 or more lenses (eyepiece and objective)uses transmitted light (light passes through object)must use thin specimen so light can pass thrucan use live specimensusually doesn’t exceed total mag. of 2000xOur scopes in class are capable of 400xonly see specimen in 2D

Compound Microscope Images

Human Hair (x 400)

Mite

Paramecium

Compound Light Microscope

Structures & Functions

Compound Light Microscope

Eyepiece/Ocular – The lens through which the scientist looks

Body Tube – Connects eyepiece to microscope

Revolving Nosepiece – Holds 3-4 objectives (magnifying lens), turns for objective selection.

Compound Light Microscope

Scanning Objective - Used for locating objects & scanning the slide quickly (Red Line- 4X)

Lowest power objective

Low Power Objective – Lens that allows you to find & center the object on a slide. Yellow line around the objective (10x)

High Power Objective - Lens that zooms in for closer viewing (40X)

Blue line around high power

Compound Light MicroscopeStage – platform upon which the slide rests

Mechanical Stage – movable clips that hold & move the slide

Iris Diaphragm – transparent lens through which light travels. Size and brightness can be adjusted.

Lamp – light source needed for viewing the specimen

Stereoscopic Dissecting Microscope

uses reflected light to produce image

range of magnification 10x-60x

Images from a Stereoscope

Penny – Abe’s face

Penny – back

Beetle

Stereo Dissecting Microscope

2 eyepieces to produce 3-D image

Uses reflected light to illuminate surface of specimen

Used on large objects which light cannot pass through

Magnifies object 5x – 60x

Electron Microscope

2 TypesScanning electron microscope (SEM)Transmission electron microscope (TEM)

Electron MicroscopeDiscovered in Germany in 1930’s and 1940’s

Uses beam of electrons to see image NOT light

Image is produced on a T.V. monitor in black & white (no light)

Much higher resolution

Limitations Can’t view living things due to vacuum in interior Very expensive Very big, must have own foundation

Transmission electron microscope (TEM)

Electrons go through very thin slice of specimen – detailed image on T.V. screen

200,000x (can be increased to 1,000,000x)

Images from a TEM

Bacteria

E.coli bacteria dividing

Leaf

Scanning electron microscope (SEM)Beam of electrons across a

whole specimen (sprayed with fine metal coating)

3 dimensional view of surface features on T.V. screen

100,000x

Scanning Electron Microscope

uses reflected electrons to produce image

Images from a SEM Dentist Drill (x 50)

Hypodermic

Needle (x 100)

Mosquito (x 100)

Toilet

Paper

(x 500)

Phase Contrast: living cells

Blood

Cheek cell

WHICH SCOPE WOULD BE BEST TO USE TO LOOK AT:

A pollen grain

Mold on a piece of bread

Bacteria

Nucleus of a cell

Grasshopper