Biological and chemical instrumentation [class one].
This class talks about instruments...
Instrument: is/are equipment used for measurement in comparison to a standard.
Instrumentation: is a study and the use of a device used for measurement, it also deals with the operation of the instrument for measurement.
Basic requirements of Instrumentation.
i. Accuracy.
ii. Reliability.
iii. Conveniency.
iv. Accessibility.
i. Accuracy: is the measure if degree of variance.
ii. Reliability: talks about the measure at which the instrument gives the right measurement, and how reliable it is.
iii. Conveniency: The equipment must be easy to use (convienient).
iii. Accessibility: The equipment must be ready for usage and easy to access.
Microscopy
Microscopy is the science of investigating small objects with an instrument called microscope or can be said to be a technical field of using microscope to view samples.
Microscope are equipment used to view samples that are too small to be seen with the naked eye.
Microscope work under the principle of illumination (brightness). Microscope gives a virtual image and not a real image because when light passes through the condenser the objective lense will magnify the sample and turn it into a real image and then the eye piece will magnify the real image into virtual image.
Microscope is divided into two systems namely;
1. Body.
2. Lense system.
1. Body: it talks about all the parts of the microscope which include;
i. Arm through which we carry.
ii. The body tube holds the draw tube and also rotating bose piece.
iii. The stage holds the sample and on it there is a hole through which light pass through and has a clip. under the stage is the;
iv. Condeser which regulates the microscope light and it's divided into sub-stage which are;
a. Condenser
b. iris diaghram
c. filter holder
and it has a
d. base and a coarse adjustment knob which raises the stage.
2. Lense system: includes;
i. the eyepiece or occular and also has different magnification that ranges from 4 - 25.
ii. It also has three objective lenses which include;
a. The Lower power
b. The High power and
c. The Oil immersion.
The low power has the magnification of 10, the high power has 40 and the oil immersion has 100. Their focal length, the low power has 1.8mm, the high power has 4mm and the oil immersion has 0.7m. Their numerical aparture for low power is 0.28 for high power is 0.7 and oil immersion does not have.
Magnification Focal Numerical
Lens Aparture
Low power 10 1.8mm 0.28
High power 40 4mm 0.7
Oil-immersion 100 0.7mm Nil
Calculation of magnification for normal microscope...
Magnification = Eye piece x magnification
iii. The condenser: regulates the amount of light that comes into the microscope, it collects the light rays from the source and focus the light on the specimen.
Ranges of Magnification
It talks about how to determine Magnification of a specimen under microscope. Under a normal microscope that has a body tube lens that has 160mm, the Magnification is the product of the eye piece Magnification by the objective lense Magnification.
Formula1. Eyepiece Magnification X objective lense Magnification
If the tube lense varies, Magnification will be the objective lense Magnification, multiply by eye piece Magnification, multiply by workpiece tube length, divided by normal tube length (which is always 160mm).
Formula2. O.L Mag X E.P Mag X working. tube length / Normal tube length.
Where;
O.L Mag = Objective lense Magnification
E.P Mag = Eye piece Magnification.
The third method is when the objective lense is marked with the focal length.
Formula3. E.P Mag X Working tube length/ Focal length of the eye-piece.
Where;
E.P Mag = Eye piece Magnification.
Class - Exercise
The Magnification of an object is 200, what is the working tube length if the eye piece and objective lense are 4 and 40 respectively.
Solution.
Parameters;
Magnification = 200
Working tube length = ?
Eye piece = 4
Objective lense = 40.
Formula2 will be used in this case.
Magnification = O.L Mag X E.P Mag X working tube length / Normal tube length.
200 = 40 X 4 X working tube length/ 160
200 = 160 Working tube length/ 160
160 divides 160 and w ehave;
200= working tube length.
So therefore;
Working tube length = 200.
Setting up a Microscope.
~ There must be enough illumination if the best result is to be obtained.
There are two (2) major methods of adjusting illumination.
1. Nelson or Critical Method.
2. Kohler method.
Mode of operation
1. Put the microscope on the table and place it at the centre of a table not the end.
2. Plug to the power source.
3. Switch on the light source.
4. Make sure low powet objective is in focus, view and make sure there is enough brightness, place the side to view on the stage and clip it down, adjust the coarse adjustment knob until the specimen is brought to focus, then adjust the fine adjustment knob until the specimen is clearly seen, adjust the iris diaghram to get bright lightning, change to high power objective lense, and then view the sample, if the oil immersion objective is used, put a drop of the oil on the sample, cover with cover slip and view.
Maintenance of a Microscope
1. Make sure the microscope is placed on the centre of the table.
2. Use lense tissue paper to clean the lenses of the microscope.
3. Don't put near a chalk board.
4. When not in use, put in a container.
5. When not in use unplug.
6. It must be cleaned regularly.
7. It must be serviced regularly.
8. Don't clean with alcohol, but benzol must be used.
9. Servicing must be done by a technician.
Thanks... please comment if you see any mistake.....
Good luck on your exams.
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