B1-Microscopy Flashcards
What is the use of microscopes
They let us see things we can’t see with the naked eye
What is the use of light microscopes and how do they work?
Light microscopes use light and lenses to form an image of a specimen and magnify it. They let us see individual cells and large sub-cellular structures eg: nuclei.
What is the use of electron microscopes and how do they work?
They use electrons instead of light to form an image. They have a higher magnification than light microscopes.
Which has a higher resolution Light microscopes or Electron microscopes
Electron microscopes, they let us see smaller things in more detail eg: the internal structure of mitochondria and chloroplasts. They even let us see tiny things like ribosomes, plasmids.
What is the formula for magnification
How to calculate image size or real size?
A specimen is 50μm wide. Calculate the width of the image of the specimen under a magnification of X 100. Give your answer in mm
Why do you use standard form when dealing with microscopes?
Because microscopes can see such tiny objects and the measurements may be very small numbers with lots of zeros which can be changed into something more manageable
What is standard form
Changing a very big or very small number into a power of 10
How do you use standard form
Any number that we can write as a decimal number, between 1.0 and 10.0, multiplied by a power of 10, is said to be in standard form. 1.23 × 108
A mitochondrion is approximately 0.0025mm long. Write this figure in standard form
How do you prepare a slide for reviewing under a microscope
1) put the specimen on a microscope slide
2) add a drop of water to the middle of a clean slide
3) cut an onion and separate it in layers
4) use tweezers peel off epidermal tissue
5) add a drop of iodine soloution (iodine sol is a stain stains are used to highlight objects in a cell by adding colour to them)
6) place a cover slip (square,thin,transparent plastic/glass) on top, to do this stand cover slip upright on slide next to water droplet then tilt and lower it so it covers specimen. try to get no air bubbles under there. They will obstruct the view of the specimen.
How to use a light microscope to look at a slide
1)Clip the slide you prepared onto the stage
2)select the lowest powered objective lens (the one that produces the lowest magnification
3) Use the coarse adjustment knob to move the stage up to just below the objective lens
4) Look down the eyepiece. Use the coarse adjustment knob to move the stage down until the image is roughly in focus
5) Adjust the focus with the fine adjustment knob until you see a clear image of what’s on the slide
6) If a higher magnification is needed swap to a higher powered objective lens and refocus
How do you draw your observations?
1) Draw what you see under the microscope using a pencil with a sharp point
2)make sure your drawing takes up at least half of the available space and that it is drawn with clear unbroken lines
3) No colouring or shading
4) if you are drawing cells the sub-cellular structure should be drawn in proportion
5) REMEMBER TO INCLUDE A TITLE OF WHAT YOU’RE OBSERVING and write down the magnification that it was observed under.
6) Label important features of your drawing eg: nucleus,chloroplasts using straight uncrossed lines
