microscopes

Question 1

differences between a light and electron microscope

Answer 1

• electron has better resolution and higher magnification, meaning they let us explore structures of cells in finer detail

Question 2

what is a slide

Answer 2

a strip of clear glass or plastic where the specimen is placed

Question 3

how do you prepare a slide to view an onion cell

Answer 3

1. Add a drop of water to a clean slide
2. Cut up an onion and separate it into layers, use tweezers to peel off epidermal tissue from the bottom of one of the layers
3. Using the tweezers, place the epidermal tissue into the water on the slide
4. Add a drop of iodine solution
5. place a cover slip on top by placing it upright on the slide, next to the water droplet, then, carefully tilting and lowering the slip so that it covers the specimen

Question 4

why is iodine solution used in the onion practical

Answer 4

its used as a stain to highlight the subcellular structures by adding colour to it

Question 5

what is the function of a cover slip

Answer 5

it prevents air bubbles

Question 6

why should you try not to get air bubbles under the cover slip

Answer 6

because they’ll obstruct your view of the specimen

Question 7

how do you use a light microscope to look at your slide after you’ve prepared it

Answer 7

1. Clip your prepared slide onto the stage
2. Select the lowest objective lens
3. Use the coarse adjustment knob to move the stage up, just below the objective lens
4. look down the eyepiece, use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
5. Adjust the focus with the fine adjustment knob until you get a clear image of the object
6. For higher magnification, turn the objective lens to a higher one

Question 8

what are the purposes of adjustment knobs

Answer 8

to move the stage upwards and downwards and improve resolution of image

Question 9

why shouldnt we look down the eyepiece when positioning the objective lens

Answer 9

we might damage the slide

Question 10

what does slowly turning the coarse adjustment knob do

Answer 10

increases the distance between the objective lens and the slide

Question 11

why do we use the epidermal layer of the onion when putting it onto the slide

Answer 11

because the epidermal layer is transparent so light can pass directly through it

Question 12

how to draw your microscope observations

Answer 12

• make sure your drawing takes up at least half the space available
• make sure that it is drawn with clear and unbroken lines
• make sure your drawing does not include any colouring or shading
• make sure the subcellular structures, if you include them, are drawn in proportion
• write down the magnification
• label the important features, eg the nucleus