Micrometry and Microscopy

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Trials

(HPO)

No. Of Stage Micrometer Divisions

No. Of Ocular Micrometer Divisions

Calibration Constant

1

2

3

1

1

1

4

4

4

2.5 um

2.5 um

2.5 um

For Table 1.2, in all three trials, the 1st line of the stage micrometer is superimposed to the 4th line of the ocular micrometer thus resulting in a value of 2.5 um. The resulting value was used as calibration constant in computing the size of the specimen in high power objective lens.

Table 1.3 Computation for the size of the specimen

Objective

Calibration Constant

No. Of Ocular Micrometer Divisions

Size

LPO

10 um

14

140 um

HPO

2.5 um

55

137.5 um

For Table 1.3, the value of the calibration constant is multiplied to the number of ocular micrometer divisions resulting to 140 um and 137.5 um for Low power objective and High power objective lens respectively.

Theoretically, the values of both objectives should result to the same computed size of the microorganism but as the table indicates, there were difference because of the errors that occurred; may be human error or inefficiency of equipment.

IV. Research Questions

1. What is the correct procedure for carrying and handling microscope? Give 10.

a. Use both hands when carrying the microscope and carry it from the base and the arm.

b. Use soft brush or pressurized air to remove the dirt.

c. Cover the microscope and return it to the correct spot.

d. The microscope must be in a clean, dry place.

e. Do not touch optical lens with bare fingers.

f. Never store a microscope in direct sunlight since sunlight can affect the quality of the specimen’s image.

g. Use only the prescribed halogen or fluorescent bulb.

h. Do not disassemble the microscope since it can cause electric shock even damage to the microscope.

i. Clean the microscope’s body and stand with moist, soft cloth with an ample amount of detergent.

j. When in moist environments, it is advisable that the microscope must be stored in a waterproof container with a drying agent.

2. What is total magnification? How it is computed?

The image that is seen through the eyepiece is magnified twice (one in the ocular lens and the other is on the objective lens) so the total magnification is computed via ocular lens magnification multiplied by the objective lens magnification.

3. What is resolving power? How do you achieve maximum resolution?

Resolving power in a lens shows two adjacent objects as two points in the image that is separated. The resolution is lost if the two objects appear as one. Increasing the magnification will only blur the given object and not increase the resolution. A certain microscope can give you high magnification but if the lenses are low quality, poor resolution may affect the image quality of the object. To achieve maximum resolution, there are certain factors to be considered. One, the numerical aperture determines the ability of the lens to gather the light and resolve a point at a fixed distance from the lens. Two, diffraction can cause a big impact on the image of the object: too much diffraction can limit the resolution of the microscope and without diffraction; the specimen will not be visible. Third, increase the refractive index between the objective lens and the specimen.

4. Calculate the total magnification of the microscope with each objective.

For Low Power Objective:

Ocular Lens × Low Power Objective Lens = Total Magnification

10 × 4 = 40x

For High Power Objective:

Ocular Lens × High Power Objective Lens = Total Magnification

10 × 10 = 100x

For Oil-immersion Objective:

Ocular Lens × Oil-immersion Objective Lens = Total Magnification

10 × 100 = 1000x

5. Give and describe the 4 optical properties of lenses.

a. Magnification is the ability of the lens to enlarge a certain specimen being observed.

b. Resolution or resolving power is the ability of the lens to determine the two objects in a specimen as two separate points.

c. Depth of field is the range of depth in the specimen.

d. Illumination is another feature that is important because higher magnification will require vast amount of light.

6. Why do compound microscopes invert the images?

The inversion of the image was caused by the rays that projected through the light crossover. Since the ocular lens only magnifies the certain image, the