Micrometry

I AM HAFIZ MUHAMMAD WASEEM from mailsi vehari
BSc from science college Multan
MSC university of education Lahore
i love Pakistan and my teachers

1. HAFIZ MUHAMMAD WASEEM BA BA G LAHORE UNIVESITY OF EDUCATION LAHORE PAKISTAN

2. Micrometry UNIVESITY OF EDUCATION LAHORE PAKISTAN

3. Micrometry It is the technique used for the measurement of microscopic objects (Organisms) . Size of microorganisms is measured using micrometers. For this purpose a microscope is required A suitable scale for the measurement of objects Micrometer

4. Types of Micrometer There are two types of micrometers: stage micrometer ocular meter or ocular micrometer

5. Ocular micrometer: Simply a disc of glass upon which etched lines There are usually etched 50 or 100 equally spaced divisions. Scale on ocular micrometer does not have any standard value It is close to the eyepiece that is why it is called ocular micrometer.

6. Continued … Stage micrometer It is a glass slide having in its center known (1mm) distance etched into 100 equal divisions Each division equals 0.01mm or 10 µm

7. A. An ocular micrometer; B. magnified ocular micrometer scale and C. L. S, of ocular to show position of ocular meter in it.

8. A. A stage micrometer ; B. Stage micrometer fixed on stage and C. magnified stage micrometer scale.

9. Principle Ocular micrometer is calibrated under different objective lenses by superimposing the graduations of stage micrometer.

10. Continued … By determining that how many divisions of ocular micrometer super impose a known distance on the stage micrometer , we can find out the exact value of one division of ocular micrometer.

11. Continued … Once calibrated ocular micrometer can be used to measure the size of different microbes

12. Experiment- example to understand : Objective: To measure the dimensions of common microorganisms by calibration and standardization of microscope using stage micrometer and ocular micrometer.

13. Continued … Requirements: Microscope, stage micrometer, ocular meter and slide of the microorganism to be measured.

14. Procedure This micrometer is used inside the eyepiece. The upper eye lens is unscrewed and the ocular meter is put into the tube of eyepiece, and the eye lens is again replaced in its original position.

15. Continued … 50 or 100 divisions in the ocular meter which are engraved on the glass. The stage micrometer is kept under low power of microscope and is observed through the eyepiece having ocular meter.

16. Continued … Suppose we have 10X objective and 5X eyepiece fitted in the microscope . At this magnification the number of ocular divisions coinciding the stage micrometer are observed and hence calculated for microns per ocular divisions.

17. Scales of stage and ocular micrometers superimposed Stage micrometer Ocular micrometer

18. Continued … e.g., let us take that 5 ocular divisions coincide with 7 divisions of stage micrometer. Therefore , 5 ocular divisions = 7 stage micrometer divisions, or 5 ocular divisions = 0.07 mm (since 1 division = 0.01 mm ). 1 ocular division = 0.07/5mm = 0.07 × 1000/5µ = 70/5µ = 14µ

19. Or, it can also be calculated by following formula: One division of ocular = Number of stage micrometer divisions/Number of ocular meter divisions × 10 In the case mentioned above it will be = 7 × 10/5µ = 14µ

20. C alibration In this way the microscope is calibrated for different combinations of eyepieces and objective lenses and is kept for record . It is to note that this calibration will be just only of the tried lenses on this particular microscope. Take three readings in this way, and the mean value of these readings will be the actual value of one part of ocular meter .

21. Record data in the following table:

22. Measurement of the Microorganisms When the microscope is calibrated , then the object or organism to be measured is kept on the stage. The object is measured in the particular magnification by ocular divisions and then is changed into microns by multiplying ocular divisions with calibrated value of one ocular division in that particular magnification .

23. Continued … Suppose the length of an object is observed to be equal to 6 divisions of ocular, so the length of this object in microns will be : 6 × 14µ = 84µ In this way the object is measured in different magnifications.

24. Fig. Diagram showing an ocular microorganism for measuring the dimensions of bacterial cells.

25. Thank you