MICROSCOPES Flashcards
What is an estimation?
an approximate value
The electron microscope was invented in 1931
What does an electron microscope use to magnify images of cells?
electrons
What does a microscope do?
magnifies small objects using lenses so they appear larger
A microscope has a ×4 eyepiece lens and
a ×3 objective lens
What is the total magnification?
magnification = eyepiece lens x objective lens
magnification = 4 × 3 = x12
How many times bigger can a light microscope magnify images of cells?
x 2,000
actual size = what / what
actual size = image size / magnifcation
a cell on a glass slide is 50μm wide
How wide is the image of the cell
under a x40 magnification?
image size = actual size x magnification
(image size = 50μm x 40)
image size = 2,000μm
What is an observation?
Looking carefully** at an _ob_ject**
How many times bigger can an electron microscope magnify images of cells?
2 million
×2,000,000
to see sub-cellular structures
total magnifcation = what / what
total mag = image size / actual size
The light microscope was invented c. 1650
What does it use to magnify
images of objects?
a light source
like the sun
Name the unit symbol for a nanometre
nanometre
nm
What unit is 1,000 times smaller than a mm?
micrometre
μm
How do you prepare an onion cell
for a microscope?
- Cut an onion and separate it into layers
- Using tweezers, peel off some onion cells and place them on a glass slide
- Using a pipette, add a drop of iodine solution to stain the cells to see them more easily
- Put a cover slip on top of the cell
What do you clip onto
the stage of the microscope?
a glass slide with an object (cells) on top
When looking at a glass slide,
how do you make the image clearer?
adjust the fine focusing knob
Why might you adjust the mirror?
You might angle it to reflect more light up through the hole in the stage
Name the largest knob on the microscope?
rough focusing knob
What do you put the glass slide on?
the stage
Why do you add a drop of iodine to the slide?
iodine stains the starch in plant cells (onion) making it easier to see the cell’s structure (nucleus, cholorplasts etc)
draw the magnifcation triangle
I
————
A x M
Image size Actual size Magnification
image size = what x what
image size = magnifcation x actual size
Name the smallest knob on the microscope
fine focusing knob
What part of a microscope do you look through?
eyepiece lens
Why do you use the rough focusing knob?
move the objective lens closer to the stage
