microscopy

disadvantages of light microscope

-limited magnification

-limited resolution

why choose electron microscope over light microscope

much greater magnification and resolution compared

-can study cells in much finer details

-enabled biologists to see and understand many more sub-cellular structures.

magnification formula

size of image / size of real object

parts of optical microscope

stage- where we place microscope slide

clips -hold the slide in place

lamp- light from lamp passes up through the microscope slide

-objective lens- the three lenses

-eyepiece- at the top of microscope and contains eyepiece lens which has magnification of 10x

-coarse focusing knob

-fine focusing knob

practical: how to view a prepared slide under an optical microscope

-first place slide onto the stage

-use clips to hold the slide in place

-we then select the lowest power objective lens and position the objective lens so it almost touches the microscope slide

-to do that slowly turn coarse focusing knob and important that we look at the microscope from the side while we adjust the position of he objective lens and when almost touches the slide, stop turning the knob

-if we look through eyepiece while positioning the objective lens, there is a risk that we damage the slide

-slowly turn coarse focusing knob which turn increases the distance between the objective lens and the slide and we do this until the cells come into focus

-use fine focusing knob to bring cells into a clear focus

-we can then select a higher power objective lens and again need to adjust fine focusing knob to bring cells back into focus

how to workout total magnification of microscope

multiply magnification of eyepiece lens by the magnification of objective lens

how to prepare a microscope slide

1. use tweezers to remove a thin layer of epidermal tissue

2. add drop of water to a clean slide

3. place epidermal tissue into the water on the slide

4. add drop of iodine to stain the cell so structures within the cell can be observed

5. place a cover slip on top of the specimen at an angle to avoid air bubbles

how to produce biological drawings:

-clear, unbroken lines

-magnification should be given

-no colouring in or sketching

give a brief history of the microscope

• Microscopy techniques have advanced over time, enhancing our understanding of subcellular structures.

  • 17th century: Development of the first light microscopes.

    • Light microscopes use light and lenses to magnify specimens, allowing visualisation of cells and large subcellular structures like nuclei and vacuoles, often with the aid of stains

    • Their design has evolved to improve magnification and resolution over time

  • 20th century: Introduction of the first electron microscopes.

    • Electron microscopes use electron beams instead of light, providing much higher resolution and magnification due to the smaller wavelength of electron beams