Microscopes

Question 1

Optical microscope

Answer 1

• uses light to form an image
• max resolution = 0.2 micrometres - cant see anything smaller than this - can see nucleus and mitochrondria - everything else too small
• max useful magnification = x1500

Question 2

Electron microscope

Answer 2

• use electrons to form image
• high max resolution = 0.0002 micrometres - gives a more detailed image vs optical light microscope.
• max useful magnification = x1,500,000

Question 3

The types of electron microscope

Answer 3

TEMs = Transmission Electron Microscope 
SEMs = Scanning Electron Microscope

Question 4

TEMs

Answer 4

• use electromagnets to focus a beam of electrons + transmitted through the specimen
• denser parts of specimen absorb more electrons = look darker on the image
• gives high resolution images so you can see internal structure of organelles like chloroplasts.
• BUT - can only be used on thin specimens.

Question 5

SEMs

Answer 5

• scans a beam of electrons across the speimen, this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
• images show the surface of the specimen and they can be 3D.
• can be used on thick specimens
  BUT gives lower resolution images than TEM’s.

Question 6

How to prepare “temporary mount” for optical microscope

Answer 6

• pipette a drop of water onto slide then use tweezers to plan thin section of your specimen on top of the water drop
• add a drop of stain
• finally add a cover slip