Lab Manual Total magnification is calculated by multiplying the magnification of the ocular lens (eyepiece) by the magnification of the objective lens. The magnitication of a lens is imprinted on the lens casing. Total Magnification Observation: Total Magnification Calculate total magnification figures for your microscope, and record your findings in Table 2.3. Total Magnification Table 2.3 Total Magnification Objective Lens Ocular Lens Objective Scanning power (if present) Low power High power Oil immersion (if presents A microscope’s field of view is the circle visible through the lenses. The diameter of field is the length of the field from one edge to the other. Field of View Observation: Field of View Low-Power (10x) Diameter of Field 1. Place a clear, plastic ruler across the stage so that the edge of the ruler is visible as a horizontal line along the diameter of the low-power (not scanning) field. Be sure that you are looking at the millimeter side of the ruler 2 Estimate the number of millimeters, to tenths, that you see along the field: mm. (Hint: Start with one of the millimeter markers at the edge of the field.) Convert the figure to micrometers: um. This is the low-power diameter of field (LPD) for your microscope in micrometers. High-Power (40x) Diameter of Fleld 1. To compute the high-power diameter of field (HPD), substitute these data into the formula given: a. LPD low-power diameter of field (in micrometers) b. LPM low-power total magnification (from Table 2.3) c. HPM high-power total magnification (from Table 2.3) Example: If the diameter of field is about 2 mm, then the LPD is 2,000 um. Using the LPM and HPM values from Table 2.3, the HPD would be 500 am. 200 um. X. X. HPD LPD xPM HPM HPD (6oh) 22 Laboratory 2 Metric Measurement and Microscopy 20
The Correct Answer and Explanation is :
Total Magnification Calculation
Total magnification is calculated using the formula:
[
\text{Total Magnification} = \text{Ocular Lens Magnification} \times \text{Objective Lens Magnification}
]
For a typical microscope:
- Ocular lens magnification = 10x
- Objective lens magnifications:
- Scanning power (if present) = 4x
- Low power = 10x
- High power = 40x
- Oil immersion (if present) = 100x
Total Magnifications:
- Scanning Power: ( 10x \times 4x = 40x )
- Low Power: ( 10x \times 10x = 100x )
- High Power: ( 10x \times 40x = 400x )
- Oil Immersion: ( 10x \times 100x = 1000x )
Field of View Calculation
The field of view (FOV) represents the visible circular area seen through the microscope. The high-power diameter of the field (HPD) is determined using the formula:
[
\text{HPD} = \frac{\text{LPD} \times \text{LPM}}{\text{HPM}}
]
Assuming:
- Low-power diameter of field (LPD) = 2000 µm
- Low-power total magnification (LPM) = 100x
- High-power total magnification (HPM) = 400x
[
\text{HPD} = \frac{2000 \times 100}{400}
]
[
\text{HPD} = \frac{200000}{400} = 500 \text{ µm}
]
Thus, under high power, the field of view is 500 µm.
Explanation (300 Words)
Microscopy allows for magnification of small objects beyond what the naked eye can perceive. A compound light microscope employs two types of lenses: ocular lenses (eyepiece) and objective lenses. The total magnification is determined by multiplying the ocular lens magnification by the selected objective lens magnification.
For example, if the ocular lens is 10x and the objective lens is 40x, the total magnification is:
[
10x \times 40x = 400x
]
This means the image is magnified 400 times its actual size.
Another crucial aspect of microscopy is the field of view (FOV), which is the visible circular area seen through the microscope. The FOV changes with magnification: at lower magnifications, a larger area is visible, while at higher magnifications, a smaller area is seen in greater detail.
To calculate the high-power field diameter (HPD), we use the formula:
[
\text{HPD} = \frac{\text{LPD} \times \text{LPM}}{\text{HPM}}
]
Given an LPD of 2000 µm under low power (100x magnification), and a high-power magnification of 400x, we calculate HPD as 500 µm. This means the visible area under high power is 500 µm across.
Understanding magnification and FOV is essential in microscopy for estimating the actual size of specimens and ensuring accurate observations. These calculations allow scientists to compare structures at different magnifications efficiently.