2.2 Size of specimens (3)
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1.
The length of a certain cell is measured as 0.15 mm. State this length in micrometres (μm). Show your working.
Answer:
Conversion: 1 mm = 1000 μm
Calculation:
0.15 mm x 1000 μm/mm = 150 μm
Therefore, the length of the cell is 150 μm.
2.
The actual size of a bacterium is 2 x 10-6 metres. A student observes the bacterium using a microscope with an objective lens of 40x magnification. Calculate the image size observed by the student. Use the formula: magnification = image size ÷ actual size.
Answer:
The formula is: Magnification = Image Size ÷ Actual Size
Rearranging the formula to solve for image size: Image Size = Magnification × Actual Size
Image Size = 40x × (2 x 10-6 m)
Image Size = 8 x 10-5 m
The image size observed by the student is 8 x 10-5 metres.
3.
A student uses a compound microscope to view a specimen. The eyepiece lens has a magnification of 10mm and the objective lens has a magnification of 40x. Calculate the total magnification of the microscope and state the size of an object that appears to be 4mm in diameter when viewed under these conditions.
Total magnification = Eyepiece magnification x Objective magnification
Total magnification = 10mm x 40 = 400x
Size of object in the specimen = (Size observed in the specimen) / (Magnification)
Size of object in the specimen = 4mm / 400 = 0.01mm = 10 micrometers
Therefore, the total magnification is 400x and the object is 10 micrometers in diameter.