Microscopes

How does the light microscope work?

The condenser lens focuses light onto the specimen. Light passes through objective lens which focuses it and can be changed in order to alter the magnification. The light passes through the eyepiece lens into the eye.

Light microscope magnification and resolution

Max Resolution: 0.2 um

Max magnification x1500

How does a transmission electron microscope work?

Electromagnets are used to focus a beam of electrons passes through a thin section of a specimen. Denser part of the specimen absorb more electrons which appear darker on the electron micrograph that is produced.

TEM resolution and magnification

Max resolution: 0.0002 um

Max magnification: x 1,000,000

How does a scanning electron microscope work?

A beam of electrons passes across the surface and scatter. This knocks off electrons from the specimen which are reflected and gathered in a cathode ray tube. The pattern of scattering builds up a 3D image depending on the contours of the specimen.

SEM resolution and magnification

Max resolution: 0.002 um

Max magnification: less than x 500,000

How does a laser scanning confocal microscope work?

Uses laser beams to scan a specimen that is tagged with fluorescent dye. The laser causes the dye to fluoresce and the light is then focused through a pinhole onto a detector, which produces an image on the computer.

Laser scanning confocal microscope resolution and magnification.

Max resolution: 0.8 um

Magnification: x 400

Light microscope advantages

• inexpensive

• small and portable

• simple sample prep

• species can be living or dead

• easy to set up

• does not use harsh chemicals

Light microscope disadvantages

• low magnification

• low resolution

Example of light microscope uses

• use light rays to observe an object

TEM advantages

• best resolution

• high magnification

• can see details inside cells

TEM and SEM disadvantages

• expensive

• can only be used in controlled environments

• specimen must be dead

• vacuum needed

• harsh chemicals used in preparation

TEM uses

used focused beams of electrons through sections of tissues

SEM advantages

High magnification and resolution

Stunning 3D images of surfaces are produced

SEM uses

Used focused beams of electrons reflected off the tissues

Laser scanning confocal advantages

• non invasive

• can see living cells

• can observe cell processes by tracking molecules

• higher resolution that light microscopes

Laser scanning confocal disadvantages

• more expensive than light microscopes

• more complex than light microscopes

Laser scanning confocal uses

• used in endoscopic procedures

• used in the development of new drugs - uses a laser beam to illuminate chemical stains within the specimen. These then fluoresce.