2.5: Diameter of Field
Measuring the diameter of field
The field is the circle of light that you observe when you look into the microscope. The diameter of this field changes as you increase magnification. There is an inverse relationship between magnification and diameter of field.
- Place a thin, clear, metric ruler on the stage. Hold it in place with the stage clip.
- Use the scan objective to focus and observe the millimeter marks on the ruler.
- Record the diameter of field using scan objective lens in mm. Include half spaces. Convert to micrometers.
- Diameter of field using low power objective lens = 1.8 mm, convert to micrometers.
- Diameter of field using high power objective lens = 0.5 mm, convert to micrometers.
Why is the diameter of the field of view considered to have an inverse relationship with magnification?
Human epithelial cell
What domain and kingdom do humans belong to?
- Obtain a flat toothpick and obtain a sample of your cheek epithelial cells from the inside lining of the oral cavity.
- Smear the cells on a clean glass slide and dispose of toothpick in biohazard trash.
- Obtain a small bottle of methylene blue dye. Make sure that the dropper does not actually touch the slide (do not contaminate the dropper bottle with your cheek cells). Let a small drop of methylene blue dye fall onto the slide.
- Place a clear cover slip on top of the specimen.
- Bring the epithelial cells into focus using the scan objective and the coarse adjustment knob. Zoom in on a few cells by using the low power objective lens.
- Confirm with your instructor that you have viewed a cheek epithelial cell.
- Switch the objective lens to high power. Sketch one cell
- Label the cell membrane, nucleus, and cytoplasm of the cell
- What is the genetic material found in the nucleus of this eukaryotic cell?
Plant Cells - Onion
What domain and kingdom do onion cells belong to?
- Remove the thin, transparent epidermis (skin) from an onion leaf. Alternately, you may view a prepared slide of onion root tip. Do not discard commercially prepared slides.
- Place on a clean slide and add a drop of methylene blue. Do not contaminate the dropper (do not touch the onion skin with the dropper). Cover with a clear slip.
- Observe with the scanning objective lens using the coarse adjustment knob first, then the fine adjustment knob.
- Observe using the low power objective lens. Make sure you see the rectangular shaped onion cells. Confirm with the instructor, if necessary. Sketch the onion cells. Be sure to indicate the total magnification used in your drawing,