Please enable JavaScript.
Coggle requires JavaScript to display documents.
1.6 Core Practical - Investigating Biological Specimens - Coggle Diagram
1.6 Core Practical - Investigating Biological Specimens
Key Terms
Clip
Stage
Objective lens
Lamp/mirror
Fine adjustment knob
Coarse adjustment knob
Eyepiece lens
Method
Place a cover slip at one end of the specimen, holding it at an angle with a mounted needle and carefully lower it onto the slide. Press it down gently so that no air bubbles are trapped under it. Then clip the slide onto the stage
Select the lowest-powered objective lens
Add a drop of stain if your specimen is completely transparent or colourless - this makes the specimen easier to see (different stains highlight different structures within cells e.g. methylene blue stains DNA
Use the coarse adjustment knob to move the stage up so that the slide is just underneath the objective lens. Then, looking down the eyepiece, move the stage downwards (so you don't accidentally crash it into the lens) until the specimen is nearly in focus
Next, take a clean slide and use a pipette to put one drop of water in the middle of it - this will secure the specimen in place. Then use tweezers to place our specimen on the slide
Then adjust the focus with the fine adjustment knob, until you get a clear image. Position a clear ruler on he stage and use it to measure the diameter of the circular area visible - your field view (FOV)
Your specimen needs to let light through it so you'll need to take a thin slice of it to start with
If you need to see your specimen with greater magnification, swap to a higher-powered objective lens, refocus an recalculate your FOV accordingly (e.g. if your FOV was 5mm then you swap to a lens that is 10 times more powerful, your FOV will now be 5mm / 10 = 0.5mm
Magnification Calculations
Actual size = image size / magnification
Total magnification = objective lens * eyepiece lens
Magnification = image size / actual size