Cell Structure: Question 8

Worked solution

Part (a): Magnification from the scale bar

A scale bar’s printed length is an image size, and its labelled value is the corresponding actual size, so the same formula applies:

magnification = image size ÷ actual size

Both quantities must be in the same units. The actual size is given in micrometres, so convert the image size from millimetres to micrometres, since 1 mm = 1000 μm:

4 mm × 1000 = 4000 μm

Now divide by the actual size:

4000 μm ÷ 1 μm = 4000

So the magnification of the micrograph is ×4000.

Part (b): Actual length of the mitochondrion

Rearranging the formula to find actual size:

actual size = image size ÷ magnification

Convert the mitochondrion’s image length to micrometres:

8 mm × 1000 = 8000 μm

Divide by the magnification found in part (a):

8000 μm ÷ 4000 = 2 μm

So the actual length of the mitochondrion is 2 μm.

Part (c): Actual width of the Golgi stack, in nanometres

Convert the Golgi stack’s image width to micrometres:

0.6 mm × 1000 = 600 μm

Divide by the magnification:

600 μm ÷ 4000 = 0.15 μm

The question asks for the answer in nanometres, so convert micrometres to nanometres, since 1 μm = 1000 nm:

0.15 μm × 1000 = 150 nm

So the actual width of the Golgi stack is 150 nm.

Final answers

• (a) Magnification = ×4000.
• (b) Actual length of the mitochondrion = 2 μm.
• (c) Actual width of the Golgi stack = 150 nm.