MeasurementSymbolUnit Metrem1m Millimetremm10 -3 m Micrometremm10 -6 m Nanometrenm10 -9 m

1mm = 1000  m 1m =  m So 1  m = m 1  m = 1000 nm So 1nm = m

This is the extent to which an object has been enlarged.

condenser lens

Magnifying an object reveals further structural detail. Although magnification can be increased ad infinitum it will not necessarily produce more detail. The amount of detail is due to the resolving power or resolution of a microscope.

Is the ability to see 2 adjacent, but separate, points as distinct entities following magnification. 0.2  m This is a major limitation of using the light microscope. The electron microscope has a higher resolution and can distinguish 2 points that are only 0.1nm apart. This is because light has a longer wavelength than electrons.

Both objects seen separately as they fall in different wavelengths Both objects seen as a single fused image as they both fall in the same wavelength light electron Light sees one point (inside one wavelength) Electron sees 2 distinct images (different waves)

ELECTROMAGNETIC

Coloured images are obtained using computer software As electrons do not show colour. TRANSMISSION ELECTRON MICROSCOPE Electrons pass through very thin specimens, giving very high resolution and therefore very high magnifications are possible

SCANNING ELECTRON MICROSCOPE Electrons are reflected off the surface of the specimen. The resolution and magnification is not as high, but SEM PRODUCES 3D IMAGES

Comparison of light and electron microscopes Light microscopeElectron microscope Radiation used Light raysElectron beams Magnification X2000X Resolving power 0.2mm0.1nm Focused by Glass lensesElectromagnets so needs vacuum as electrons deflected by air Bio material Living or deadDead (in vacuum) Prep of material Quick & simpleTime consuming complex: special cutting apparatus needed & special stains. This may lead to distortion of the bio material forming artefacts. Highlight the advantages and disadvantages of each type of microscope

I = IMAGE SIZE M = MAGNIFICATION A = ACTUAL SIZE Calculating magnification, image and object size from a micrograph MAGNIFICATION = IMAGE SIZE ACTUAL SIZE

1.An object on an electronmicrograph is measured as 12mm, but has an actual size of 2.3 m m. Calculate the magnification. 2.An organelle measures 21mm at a magnification of X Calculate the actual size of this organelle. 3. An organelle has an actual size of 0.7 m m. Calculate the image size when it is magnified X

Measure the length of the scale bar in mm This is the image size. Read the length given on the scale bar This is the actual size Find the magnification Use the equation M = I/A

Preparation and staining of temporary mounts

Making microscope drawings Clear and accurate sharp pencil line drawingsClear and accurate sharp pencil line drawings No shading or colourNo shading or colour Label clearly and accuratelyLabel clearly and accurately Plan your drawing ensure parts are in proportion and fit pagePlan your drawing ensure parts are in proportion and fit page Draw a faint outline showing relative position of partsDraw a faint outline showing relative position of parts Complete final outline and details with clear firm lines.Complete final outline and details with clear firm lines. Be as accurate as possibleBe as accurate as possible Ensure labels are added in pencil and not too close to the drawingEnsure labels are added in pencil and not too close to the drawing