Biology 20

Unit One: Matter and Energy Flow in Cells

Topic Two: The Microscope

Objects that can be observed by the Objects that can be observed by the unaided eyeunaided eye

Objects that can ONLY be viewed Objects that can ONLY be viewed using a microscopeusing a microscope

IntroductionIntroduction• The cell is the unit of structure of all

living things. Living organisms include: – Plants– Animals– Bacteria– Protists– Fungi

• All living things are made of at least ONE cell

• Hundreds of years ago, no one knew this because cells were too small to be seen with the unaided eye

• The creation of the MICROSCOPE proved the existence of cells!!!

MicroscopesMicroscopes1.Why do we use microscopes?

– microscopes magnify objects and make small things appear larger

2.What is the main benefit of using microscopes? - resolution or the ability to see detail

• 3 main types of microscopes:– Light/compound microscope– Transmission Electron Microscope

(TEM)– Scanning Electron Microscope (SEM)

Ocular Lens

Objective Lens

3. How do we calculate the total magnification of

an object using a light microscope?

Total magnification = magnification of ocular lens x magnification of

the objective lens

10X

40X

Total mag. = 10 x 40 = 400 times

1. Light Transmission Microscope1. Light Transmission Microscope• Total Magnification:1000X • The image is produced bylight passing through the specimen• The qualities of the image produced

are: color and 2-D

Light Transmission MicroscopeLight Transmission MicroscopeAdvantages of the light

microscope include:– color image– living material may be used

Disadvantages include: – low magnification– poor resolution at higher

magnifications as the light rays are bent (large images but little detail) http://www.youtube.com/watch?

v=7pR7TNzJ_pA&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

Amoeba moving video

Scanning Electron Microscope

Scanning Electron Microscope• TotalMagnification: 500,000X• Scans the surface of the

specimen• The image is produced byElectrons reflected off the surface• Often coat specimen with gold

for a sharper image

Scanning Electron Microscope Scanning Electron Microscope • The qualities of the image are: • 3D, black and white picture of the surface

of the specimen.• Advantages: • high magnification• 3D image that can be easily understood• Disadvantages: specimen must be dead

Transmission Electron MicroscopeTransmission Electron MicroscopePhillips CM 10 TEM

Mitochondrionimage taken by a

TEM

Transmission Electron Microscope• Total Magnification: 1,000,000X• The image is produced byelectrons passing through the

specimen– shorter wavelength than visible

light– less scatter - sharper image

• Qualities of the image are: 2D, high resolution, black and white

Transmission Electron MicroscopeAdvantages:

– Highest magnification and high resolution

– the internal detail of cell can be seen

Disadvantages: – 2-D image – black and white image– the specimen must be dead;

uses very thin slice of the specimen

– image is difficult to understand

Light Microscope

Scanning Electron Microscope

Transmission Electron

Microscope

TEM Microscope

SEM ImagesSEM Images

Bed Bug

SEM ImagesSEM Images

House Fly

More SEM imagesMore SEM imagesImage of a spider’s

leg

Various blood

cells

More SEM imagesMore SEM imagesMoth

1.Ocular lens magnifies

10X2. Body tube

3. Arm

4. Revolving nose piece

5. Stage clip

6. Objective lenses magnify 4x, 10x and 40x7. Adjustment

knob8. Slide

9. Stage10. Coarse adjustment knob (low power)13. Fine

adjustment knob

12. Light

14. Power switch15. Base

11. Iris Diaphragm

Microscope parts and functions Part Part

##Part Part

NameNamePurpose of PartPurpose of Part

11 Look through this to see an object under the microscope. Usually 10X magnification.

22 Connects the ocular to the microscope.

33 Connects the base and the barrel.

44 Turns to change the objective lenses to use.

55 Holds the slide in place

66 Used to view objects at three different magnifications

77 Moves the stage side-to-side, or forward and back to get the object into the field of view

Ocular lens

Body Tube

Arm

Nose piece

Stage Clip

Objectivelens

Stageadjustment

knob

Microscope parts and functionsPart

#Part

NamePurpose of Part

88 Piece of glass onto which the object to be viewed is placed

99 Holds the slide for viewing

1010 Raises and lowers the stage for focusing under low power

1111 Adjusts the amount of light entering the field of view

1212 Source of light

1313 Slightly moves the stage to sharpen the image

1414 Turns the illumination on or off

1515 Supports the microscope

Slide

Stage

Coarsefocus

Irisdiaphragm

Lamp

FineFocus

PowerSwitch

Base

How To Use a MicroscopeHow To Use a Microscope1. Make sure the objective lens with the lowest

power is in place.

2. Place the slide on the stage and secure the slide using the stage clip.

3. Use the coarse focus knob to bring the objective lens close to the slide. Use the fine focus knob to focus.

4. To move to high power, rotate the nosepiece to the high power objective lens. Use the fine adjustment knob to bring the image into focus.