Question

Using electron microscopes to research cells

The below photograph was taken using an electron microscope and shows a small part of a plant cell.

Electron microscopes are used to produce magnified images of cell components. The magnification of an image is how much larger it is than the actual structures. Work out the magnification of this photo by following these steps:

a) Use a ruler to measure the diameter of the nucleus in the photo. Do this in millimeters, not centimeters.

b) Convert the diameter in millimeters to micrometers.

c) Divide the diameter of the nucleus in the photo by its actual diameter, $3.3 μm$ . Be sure that both diameters are in micrometers. The value that you have calculated is the magnification of the photo.

Accepted Answer

a) The electron microscope uses a beam of electrons to visualise cellular structures. They provide high resolution (provide clearer and more detailed images) and high magnification (can detect smaller structures) than light microscopes.

The actual size for a book PDF page is typically $100 %$ .

Therefore, by measuring the diameter of the nucleus in the micrograph given in the book $= 44$ millimeters

b) We know that, $1 millimeter (mm) = 1000 micrometers (μm)$

$∴ 44 mm = X μm ∴ X = 44 \times 1000 ∴ X = 44000 μm$

Thus, the diameter of the nucleus in the micrograph in micrometers is $44000 μm$ .

c) Most of the cell size of living beings are measured in microns. Thus, the cells are too small for the naked human eye to see, unless we use a lens or a microscope. It is through the lens of the microscope that the image of an object can be magnified and observed in detail. A convex lens makes a small object look bigger than it actually is. This is called magnification.

Given,

The diameter of the nucleus in the photo (Image size) $= 44000 μm$

The actual diameter of the nucleus (Actual size) $= 3.3 μm$

The general formula for calculating magnification is:

$Magnification = \frac{Image size}{Actual size}$

$Magnification = \frac{44000}{3.3} Magnification = 13, 333.3 X$

Therefore, the magnification of the photo is $13, 333.3 X$ .

Important Questions on Cells

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