Microscope

Light microscope:

  • use light and lenses to form a magnified image of a specimen

  • images of cells and large subcellular structures are visible

  • used to study living cells and for regular use when relatively low magnification and resolution is enough

Practical - preparing light microscope slides

  • Put a thin sample of tissue (e.g. onion skin) onto a microscope slide.

  • Add a few drops of a suitable stain/dye (e.g. iodine).

  • Place a coverslip on top of the tissue and place the slide onto the microscope stage.

  • Use the objective lens with the lowest magnification, and focus on the sample.

  • Increase the magnification and refocus to see different features of the cell.


light microscope diagram


Electron microscope:

  • Electron microscopes use beams of electrons, rather than light, to visualise specimens

  • The wavelength of an electron beam is much smaller than that of visible light, which gives electron microscopes a much higher resolution and magnification

  • provide higher magnifications and higher resolution images but cannot be used to view living cells

  • There are 2 types of electron microscope:

    • the transmission electron microscope (TEM) is used to examine thin slices or sections of cells/tissues

    • the scanning electron microscope (SEM) has a large depth of field so can be used to examine the surface structure of specimens

units of measurement