calculate the length and width of each in μm. (If the cell is round, measure its diameter. If there is more than one cell present, measure the cell indicated by the arrow. Again, it may be easier to measure with a piece of paper and then compare to the micrometer below). Note: we do not want these measurements in ocular units. Be sure convert your O.U. into μm based on the objective used and the calibration factor in TABLE 2. Enter your data in the TABLE 3.
The Correct Answer and Explanation is :
To determine the length and width of cells in micrometers (µm) using an ocular micrometer, follow these steps:
- Calibrate the Ocular Micrometer:
- Align Scales: Place a stage micrometer (with a known scale, typically 0.01 mm per division) on the microscope stage. Focus the microscope so both the ocular and stage micrometer scales are visible and align them parallel to each other.
- Determine Calibration Factor: Identify two points where the scales align. Count the number of divisions on both scales between these points. The calibration factor (CF) is calculated as: CF = (Number of Stage Divisions × Stage Division Length) / Number of Ocular Divisions For example, if 20 ocular divisions align with 30 stage divisions, and each stage division is 10 µm: CF = (30 divisions × 10 µm) / 20 divisions = 15 µm per ocular division
- Measure the Cell:
- Focus on the Cell: Replace the stage micrometer with the slide containing the cell. Focus on the cell indicated by the arrow.
- Align and Measure: Align one edge of the cell with a line on the ocular micrometer. Count the number of ocular divisions spanning the cell’s length and width (or diameter if the cell is round).
- Calculate Actual Dimensions:
- Apply Calibration Factor: Multiply the number of ocular divisions by the calibration factor to obtain the cell’s dimensions in micrometers. Cell Dimension (µm) = Number of Ocular Divisions × Calibration Factor For instance, if a cell spans 10 ocular divisions and the calibration factor is 15 µm per division: Cell Dimension = 10 divisions × 15 µm/division = 150 µm
- Record Data in Table 3:
- Enter Measurements: Document the objective used, calibration factor, and the calculated length and width (or diameter) of each cell in Table 3.
Example Entry for Table 3:
| Objective | Calibration Factor (µm/division) | Length (µm) | Width (µm) | |———–|———————————-|————-|————| | 40X | 2.5 | 100 | 50 |
Important Considerations:
- Objective-Specific Calibration: Calibration factors vary with different objectives due to magnification differences. Calibrate each objective separately.
- Measurement Accuracy: Ensure precise alignment and counting of divisions to maintain measurement accuracy.
- Regular Calibration: Regularly calibrate the ocular micrometer to account for any potential discrepancies over time.
By following this method, you can accurately measure cell dimensions in micrometers, facilitating precise data recording and analysis.