Microscopes Flashcards
What do we need microscopes for?
To study most cells
What are the two types of microscopes?
Light and electron
When is light microscopes used?
When relativity low magnification and resolution is enough
What are light microscopes used to study?
Living cells
What type of microscope is for regular use?
Light
What do electron microscopes provide higher than light microscopes?
Magnification and resolution images
What can’t electron microscopes be used to view?
Living cells
What happened in the 1590s to develop light microscopes?
Janssen experimented with putting lenses in tubes- the first compound microscope.
How magnified we’re the 1590s compound microscopes thought to have magnified to?
3x to 9x
What happened in 1650s to develop light microscopes?
British scientist Robert Hooke observed and drew cells using a compound microscope
What happened in the late 1600s to develop light microscopes?
Antonio can Leeuwenhoek constructed a microscope with a single spherical lens
How magnified was the late 1600s microscope?
X275
What’s the maximum magnification of a light microscope today?
X2000
How magnified are light microscopes usually used in schools?
X400
Name the components of a light microscope
Eyepiece
Coarse focus
Objective lenses
Stage clip
Condenser
Mirror
Fine focus
Arm
Stage
Give the formula for calculating the magnification of light microscopes
Magnification of the microscope=magnification of the eye piece X magnification of the objective
If the magnification of an eye piece is x10 and the objective is x4, what’s the magnification of the microscope? Give working out
10 X 4 = 40
Give the formula for calculating magnification
Magnification= size of image/real size I object (I= a/m) (I AM)
If the real size of a cell is 0.05mm and the real size is 100mm, what’s it’s magnification? Give working out
100/0.05=2000mm
What’s the aim for preparing light microscope slides?
To prepare and stain cells for examination with a light microscope
What’s the small square of circle of thin glass called that’s placed over the specimen?
Coverslip
What’s does the coverslip do?
Prevents the slide from drying out when it’s being examined
What’s does iodine do?
Stain plant cells to make the internal structures more visible
What dye is used to stain cheek cells?
Methylene blue
Name the risks of a light microscope (preparing a slide) practical
-care must be taken when looking down the microscope if the illumination is too bright
-care when using microscope stains
-care when handling coverslips and microscope slides
What do electron microscopes use to work?
A beam of electrons
Why can’t living cells be observed using an electron microscope??
Samples are placed in a vacuum
What are the two types of electron microscopes?
Transmission electron microscope (TEM)
Scanning electron microscope(SEM)
What is the TEM microscope used to examine?
Thin slices or sections of cells or tissues
What is the SEM microscope used to examine?
Surface structure of specimens
Why can the SEM microscope be used to examine the surface structure of specimens?
It has a large depth of field
What’s the TEMs maximum magnification?
X1000000
What’s the limit of a TEM?
Less than 1nm
If we’re comparing the size of a bacteria cell with a HIV. The bacterium is 1000nm and the HIV is 100nm. Work out the size difference.
1000nm/100nm= 10
The length of the bacterium is 10 times that of the HIV
What do magnitudes go up in?
Factors of 10
Give examples of numbers in the magnitude 10^2
200,300
Give examples of numbers in the magnitude 10^3
2000,3000
What’s the aim/s of the practical- analysing biological specimens using microscopes?
-to use a light microscope to examine animal and or plant cells
-to make observations and draw scale diagrams of cells
Give the method for analysing biological specimens using microscopes.
1) rotate the objectives so that the low power objective lens(eg. X10)is in line with the stage
2) turn the coarse focus to adjust the space between the stage and the objective lens
3)place the microscope slide on the stage. Line it up so that the specimen is in the centre of the stage, where the light passes through
4) focus the slide by turning the coarse focus adjustment
5) draw a low power image. Rotate the objectives do that the high power objective(eg.40) is in line with the stage
6) bring the slide back into focus using the fine focus adjustment. If you don’t succeed, go back to low power and re-focus and start again
Name the risks of doing the analysing biological specimens using microscopes practicals
-care must be taken when looking down the microscope- illumination is not too bright as eye damage could be caused
-using some microscope stains as some are harmful
-handling coverslips and microscope slides-broken glass could cut the skin
Give the method to measure cell size
1) place a stage micrometer on the stage of the microscope
2) line up one of the division on the eyepiece graticule with a fixed point on the stage micrometer
3) count the number of divisions on the eyepiece graticule that correspond with a set measurement on the stage micrometer.
4) calculate the distance in micrometers of one division on the eyepiece graticule
