Microscopes

magnification formula

magnification = image/real object

magnification definition

How many times larger the image is

Resolution definition

The ability to see individual objects as separate entities

light microscope advantage/disadvantage

Line shone through a specimen.

ADVANTAGE:

• cheap

• can observe living/moving specimens.

DISADVANTAGE:

• limited magnification

• limited resolution

electron microscope

Electrons fired at a sample, electrons scatter and creates image.

ADVANTAGE:

• powerful magnification

• fine resolution

• can see subcellular structures.

DISADVANTAGES:

• cant view anything living

• expensive

Transmission electron microscope

2D images generated.

• high resolution.

• organelle must be dead.

• Black and white pictures produced

Scanning electron microscope

3D images produced. (surfaces)

• high resolution

• high magnification

• black and white pictures produced

staining

• increases contrast between different cell structures so they can be seen more clearly and specific cells/tissues can be identified.

types of stains

• iodine: blue/black if starch present.

• methylene blue: blue if collagen present.

• congo red: red due to plant cell walls

air bubbles risk

• obscure view so detail cant be seen easily

how to avoid air bubbles

• cell/tissue placed flat on slide with stain.

• coverslip held at an angle just touching stain

• once liquid touches, gently/slowly lower down slip.