A Level Bio Microscopes

Magnification - how large the image is compared to the real life specimen

Magnification = image size/object size

Resolution - How detailed the image is, how well a microscope distinguishes between two points that are close together

Centimetre                                                                                                                                              x10                                                                                                         Milimetre                                                                                                                                               x1000                                                                                                                   Micrometre (um)                                                                                                                                     x1000                                                                                                                   Nanometre 9nm)

Light Microscopes use light and several lenses to magnify a sample

• light from the condenser lens, then passes through the specimen, where certain wavelengths are filtered to produce an image
• then passes through the objective lens which focuses it and can be changes to change magnification
• passes through the eyepeice lens, which can also be altered to change the magnification

Max. Magnification = x1500

Max. resolution = 200nm (due to the wavelength of light)

Uses: Identify different bacteria types

Advantages: - can use live specimen - colour - easy to use - cheap

Disadvantages: - Limited resolution due to wavelength of light - low mag - have to use a                                      thin specimen

Electrons have a lower wavelength of light so can be used to produce an image with higher resolutions.

Transition Election Microscope

• - large and expensive - thin specimen - operation requires training - false colour images - specimen are dead

:Advantages - most pwerful microscopes - high quality detailed images

Disadvantages: - large and expensive - thin specimen - operation requires training - false colour images - specimen are dead

Resolution = 1nm

Magnification = x500,000

Scanning Electron Microscopes

• Electromagnetic coils pull the electron beam back and forth, scanning the specimen
• Electrons bounce of the speciment and are directed at a screenthat creates the image

Advantages: - sharp, 3d images

Disadvantages: - less powerful than TEM - false colour imaging - only deam specimen

Resolution = 1nm

Magnification = x200,000