2.2 Size of specimens

Question 1

The formula for magnification is:

Answer 1

Magnification = Image size ÷ Actual size

Question 2

How can you calculate the actual size of a specimen if you know the image size and magnification?

Answer 2

Use the formula:
Actual size = Image size ÷ Magnification

Question 3

How can you calculate the image size of a specimen if you know the actual size and magnification?

Answer 3

Use the formula:
Image size = Magnification × Actual size

Question 4

How do you convert between millimetres (mm) and micrometres (μm)?

Answer 4

1 cm = 10 mm

1 mm = 1000 μm

1 μm = 0.001 mm

Question 5

If you have a magnification of x 500, and the image size is 5 mm, what is the actual size of the specimen?

Answer 5

Use the formula:
Actual size = Image size ÷ Magnification
Actual size = 5 mm ÷ 500 = 0.01 mm

Question 6

A student measures the image of a cell under a microscope and finds it is 32 mm wide. The magnification is x 100. What is the actual width of the cell?

Answer 6

Actual size = Image size ÷ Magnification
Actual size = 32 mm ÷ 100 = 0.32 mm

Question 7

What is the unit for magnification?

Answer 7

Magnification does not have units. It is simply written as “x” (e.g., x 100).

Question 8

What is the size of the image of a specimen if the actual size is 0.2 mm and the magnification is x 500?

Answer 8

Use the formula:
Image size = Magnification × Actual size
Image size = 500 × 0.2 mm = 100 mm

Question 9

What is the actual size of a specimen in micrometres (μm) if its image size is 200 μm and the magnification is x 50?

Answer 9

Use the formula:
Actual size = Image size ÷ Magnification
Actual size = 200 μm ÷ 50 = 4 μm

Question 10

Convert 0.004 mm to micrometres (μm).

Answer 10

Use the conversion:
1 mm = 1000 μm
0.004 mm = 0.004 × 1000 = 4 μm

Question 11

Convert 250 μm to millimetres (mm).

Answer 11

Use the conversion:
1 μm = 0.001 mm
250 μm = 250 × 0.001 = 0.25 mm