A) Using the information in class, and your own research, define the terms ‘CLARITY’, ‘RESOLUTION’ and MAGNIFICATION,’ and complete the following table:
TYPE OF MICROSCOPE
Compare and Contrast Properties
Clarity can be understood as the ability to see clearly what you are looking for. This can be effected by light or contrast. Light microscopy is limited by its ability to focus on very small objects and can leave the viewer with a blurred and unrecognisable image. Clarity is also assisted by the resolution offered by a microscope, this is where electron microscopes have the advantage of light microscopy.
The downsides to electron microscopy can be the lack of colour (only black and white) and that no living organism can be monitored due to the nature of the process (i.e. vacuum, electron beam and sodium, potassium requirements). Often the subject also needs to be coated in metals like gold. Also the specimen would need to be fully dehydrated as hydrogen molecules deflect the electrons when using TEMs.
Resolution can be explained as the ability to distinguish two very small, closely-spaced objects as separate entities. This is where electron microscopes are able to show the detail of very small objects that light microscopes may often fail to capture
This is due to electrons travelling direct to the object rather than operating in a wavelength where a smaller focal point in light microscopy could be missed at higher magnification.
Magnification is the ability to zoom in on, or visually enlarge a small abject or part of an object and is often seen referenced like 100x – 600x.
Electron microscopes can magnify an object up to 2 million times. This can be done via either a scanning or transmission electron microscope. This ability of the electron microscope means it has greater use in research and forensics. The SEMs can even look past the surface of the object to assist in the understanding of its composition.
Kim, Oliver (2013)
Beneficial elements of light microscopy are that of colour and cost. Clarity can be gained by using suitable lighting for the subject and dyes to define the parts of what you’re exploring. Though limited by its ability in magnification, images can be brought into sharp focus giving the viewer sharp, crisp image where it easy to define the elements of the subject you are exploring.
There are however many factors that affect light microscopy, some of these are focal length, contrast and light that can pass through the object. Occasionally stains like methylene blue are used to highlight areas of an object to enhance the subject matter and cell characteristics like the membrane.
Wolniak, Stephen. (2004)
The resolution of a light microscope is lower than an electron microscope due to the limits that the wavelengths of light pose. This is also in part due to the detail lost through magnification using the current technology
(This means it would limit its ability to distinguish between two points in high magnification). You have a similar principle when using cameras or monitors. Often the amount of pixels used or that are visible to the eye can give a greater or lesser resolution due to the detail shown.
Light Microscopy is limited by wavelength. Even when using light in a high frequency you are still limited to a maximum of up to 2000 x magnification.
There are new advancements in this technology on a regular basis. Take for instance the lens-free optical tomographic microscope. This uses a highly sensitive digital sensor array like what you have in a digital camera placed 4mm from the object which is the illuminated and rotated to give a 3D image of the subject
Kim, Oliver (2013)
(B) In the table below, fully label the cell shown here and outline the functions of each organelle.