Microscopes

Magnification

The magnification of a microscope refers to how many times larger the image is compared to the object

Resolution

The resolution of a microscope is the minimum distance between two objects in which they can still be viewed as separate

Determined by wavelength of light and the wavelength of beam of electrons

Optical microscope

Poor resolution due to long wavelength of light

Small organelles are not visible

Living samples can be used and a colour image can be obtained

Transmission Electron microscopes

Hass to be in a vacuum and nonliving specimens can only be used

thin specimens are stained

Beam of electrons passed through specimen some parts absorb electrons and appear dark

Images 2-D and is black-and-white but control detail images on internal structures of cell

Scanning electron microscope

Specimens do not have to be as thin

electros are beamed onto surface and scattered in different ways depending on contours

Producing 3-D image

Magnification calculations

Image size = Actual size X magnification

Metres to millimetres X 1000

Millimetres to micrometres X 1000

Micrometres to nanometres X 1000

Eye piece Graticule

Full calibration stage micro meter is used to calibrate the eye piece graticule. This is a glass slide with a scale and you placed on the stage.

the scale on the stage micrometre is typically 2 mm long and the subdivisions are 10 micro meters apart

Step one- lineup the stage micrometre and eye piece graticule whilst looking through the eye piece

Step two – count how many divisions are on the eye piece graticule fit into One division on the micrometre scale

step three – each division on the micro meter is 10 micro meters so this can be used to calculate what one division on the eye pice graticule is at that current magnification