Each magnification: The long: We need to look at 40X. Know the size of 1 ocular micrometer. The size of an easiest way to do this is to measure unit (ocular the field of ocular units changes with how many ocular units there are in view did (they are inversely magnification exactly the same way as the diameter proportional): the example below magnification; MIM Is mm I$ equivalent to Cquto tont t0,54 ocular units. With our microscopes at 40X total 40 ocular units; in the microscope millimeter ruler 12. At 40X, Imm 40 ocular units ocular unit (ou) 0.025 13. Complete the table below. Total Magnification 40X Size of 1 ocular unit (um) 25um JQun 25um um 10X 400X 100
The Correct Answer and Explanation is:
📊 Completed Table: Size of 1 Ocular Unit at Each Magnification
| Total Magnification | Size of 1 Ocular Unit (µm) |
|---|---|
| 40X | 25 µm |
| 100X | 10 µm |
| 400X | 2.5 µm |
| 1000X | 1 µm |
📘 Explanation
When using a compound light microscope equipped with an ocular micrometer, it’s crucial to determine the actual size of the specimen by calibrating the ocular scale. The ocular micrometer itself is a scale inside the eyepiece that has arbitrary units (ocular units or OU) and has no fixed size. Its value changes depending on the objective lens used, which alters the total magnification.
To determine the true size of 1 ocular unit, a stage micrometer is used. This is a glass slide etched with a known scale (typically 1 mm divided into 100 parts, so each division equals 10 µm). The goal is to line up the stage micrometer with the ocular micrometer under a particular magnification and measure how many ocular units correspond to a known micrometer length.
For example, if under 40X total magnification, 1 mm (or 1000 µm) on the stage micrometer equals 40 ocular units, then:Size of 1 OU=1000 μm40 OU=25 μm/OU\text{Size of 1 OU} = \frac{1000\ \mu m}{40\ OU} = 25\ \mu m/OUSize of 1 OU=40 OU1000 μm=25 μm/OU
Because magnification and the apparent size of the field of view are inversely proportional, as total magnification increases, the size of each ocular unit decreases proportionally. Hence:
- At 100X: 25 μm2.5=10 μm/OU\frac{25\ \mu m}{2.5} = 10\ \mu m/OU2.525 μm=10 μm/OU
- At 400X: 25 μm10=2.5 μm/OU\frac{25\ \mu m}{10} = 2.5\ \mu m/OU1025 μm=2.5 μm/OU
- At 1000X: 25 μm25=1 μm/OU\frac{25\ \mu m}{25} = 1\ \mu m/OU2525 μm=1 μm/OU
This calibrated information allows accurate measurement of microscopic structures. Each time a different objective is used, recalibration is necessary unless the microscope has been previously calibrated for those objectives.
