Microscopes

help us see small objects typically less than 500 nm

nm = nanometer = 1/1,000,000 mmsize of a human eggsize of a sharp pencil point

Magnification making an image appear larger than its actual

sizenot actually changing the size of the object

Magnification indicated by _____ X

i.e. an object that is 100X had been magnified 100 times

the bottom image is 1860X

Resolution

the ability to distinguish the details of an image

measure of the clarity of an image

Resolution

improved by adjusting the focus of a microscope

resolution capability of a microscope of may be determined by an object’s size and degree of detail

Resolution

often displayed as a distancea smaller distance means that a smaller object

can be viewed clearlya smaller distance means the microscope has

better resolution

Magnification and Resolution

Both high magnification and good resolution are necessary to see small objects clearly.

Types of Microscopes

1. Compound Light Microscopes

2. Electron Microscopes

1. Compound Light Microscopes (CLM)

compoundmore than 1

lightilluminating the object

for clarity

light passes through two lenses to produce an enlarged image of a specimen

1. Compound Light Microscopes (CLM)

What is the possible compounded magnification of these lenses?

magnification of an object observed using this microscope is the multiplication of the 2 (or more) lenses used to view the object

1. Compound Light Microscopes (CLM)

2. Electron Microscopes

microscopes shoot electrons at dead objects/specimens

as the electrons bounce back, the energy is recorded and translated into an image

2. Electron Microscopes must be

viewed in a vacuumvacuum

○ no airno living cells

can be viewed

2. Electron Microscopes

There are two types of Electron Microscopes1. Transmission electron microscope (TEM)

2. Scanning electron microscope (SEM)

Transmission Electron Microscope (TEM)

Form 2D images

TEM images are always in black and white.

with the help of computers scientists add color to make things easier to see

Transmission Electron Microscope (TEM)

An electron beam is directed at a slice of a specimen that has been stained with metal ions.

Some structures become more heavily stained than others. Those heavily stained areas absorb electrons and in the lightly stained areas the electrons pass through hitting a fluorescent screen and forming an image on the screen.

Transmission Electron Microscope (TEM)

Scanning Electron Microscope (SEM)

essentially works the same as a TEM (electron beams)

shows 3D images of the surface of a specimen

Scanning Electron Microscope(SEM)

Strain of Staphylococcus aureus bacteria (20,000x)

sample is coated with a very thin layer of metal

again, color has been added with a computer

Scanning Electron Microscope(SEM)

Comparing Magnificationand Resolution

Microscope Type

Magnification

Resolution

CLM 2,000 x 200 nmTEM 50,000,000 x 50 pmSEM 500,000 x 1 nm

(1 nm = 1,000 pm)nm = nanometer (1 nm =1 billionth of a meter)pm = picometer (1 pm = 1 trillionth of a meter)

Microscope Collage

See Microscope Collage rubric.

Other Resources to use:Textbook

○ Pages 50 – 54