Microscopes Flashcards
Define the term ‘magnification’
The number of times larger an image appears, compared to the size of the original object
Define the term ‘organelles’
Small structures that are within cells - each of which has a specific function
Define the term ‘photomicrograph’
Photograph of an image seen using an optical microscope
Define the term ‘resolution’
The ability to be able to distinguish between two points clearly
The clarity of an image
Define the term ‘electron micrograph’
Photograph of an image seen using an electron microscope
What type of magnification do microscopes produce?
Linear magnification
List four reason as to why optical microscopes are still used in schools
cheap
easy to use
portable
used to study whole and living specimens
Explain simply how optical microscopes work
They relay on lenses to focus a beam of light
What is the maximum magnification of an optical microscope?
X1500
Explain why list microscopes can not magnify any higher than around X1500 effectively
As their resolution is limited - they cannot magnify any higher whilst also producing clear images
What is the maximum resolution of optical microscopes?
200 nm
What type of light does optical microscopes use?
Visible light
What are the four types of microscopes?
Optical
Laser Scanning
Scanning Electron
Transmission Electron
Explain why ribosomes cannot be seen using an optical microscope?
They are about 20nm diameter so are smaller than the resolution of the optical microscope (200nm)
Explain how to use light microscope
Place specimen onto the stage
Lens is placed over the specimen
Use the knob to focus the image while looking in the eyepiece
While viewing the image adjust the iris diaphragm for optimum light
Change the objectives X10 X40
Look at the specimen
What is the formula for calculating the total magnifying power of an optical microscope?
total magnification = objective lens magnifying power X magnifying power of the eyepiece lens
How do modern digital microscopes display their image?
On a computer screen
What is the alternative name for laser scanning microscope?
Confocal microscope
Explain how laser scanning microscopes work
They use laser light to scan an object point by point and assemble the pixel information by computer, on a computer screen.
The images produced by a laser scanning microscopes are high …. and show high…….
Resolution
Contrast
Laser scanning microscopes have a special feature
what is it?
Depth selectivity
Explain what depth selectivity is
It mean they can focus on structures at different depths within a specimen. It makes it useful to observe full and living specimens as well as cells
What are the two main plans where laser scanning microscopes are used?
The medical profession and biological research
Describe an example of how laser scanning microscopes are used in the medial profession
They’re used to observe fungal filaments in the cornea of the eye of a patient with a fungal corneal infection
This gives a swift diagnosis - therefore, giving a more effective treatment
What are the two types of electron microscopes?
Transmission Electron
Scanning Electron
What is the maximum resolution of a laser scanning microscope?
X2000
Explain how an electron microscope works
They use a beam of fast travelling electrons that are fired from a cathode and focused by magnets
Explain the types of images produced by electron microscopes?
They give clear and highly magnified images, especially compared to optical microscopes
In preparation for use of a TEM microscope, explain what has to happen to the specimen in preparation
The specimen has to be chemically fixed by being dehydrated and stained
Explain how transmission electron microscopes work
The beam of electrons shot by the cathode pass through the specimen and some of the electrons pass through and are focused onto the screen/photographic plate
Explain the electron micrography that TEM’s produce
They form a 2D black and white images
What is the maximum magnification formed by TEM’s?
X 2 million
Explain how SEM microscopes work
The electron shot by the cathode don’t pass through the specimen as the electrons bounce off and are focused on screen
Explain the image that SEMS give
The images that re produced re black and white and are 3D
Computer software programmes can also ass false colour
List three disadvantages that are with both types of electron microscopes
Very expensive
Very large
Need training and skill to be able to use them
Specimens used for electron microscopes have t be …. when used in the microscopes
Dead
What are the effects the metallic salt stains used for staining can have on humans?
They can be potentially hazardous for humans
