Size of specimens Revision Notes

Magnification is calculated using the formula: Magnification = Image size ÷ Actual size. Both sizes must be measured in the same units, such as millimetres or centimetres, to ensure accuracy.

• Magnification = Image size ÷ Actual size.
• Units must be the same for image and actual size.
• Magnification indicates how many times larger or smaller the image is.

- If magnification is greater than 1, the image is larger than the object.

- If magnification equals 1, the image and object are the same size.

- If magnification is less than 1, the image is smaller than the object.

• Magnification > 1: image enlarged.
• Magnification = 1: image same size.
• Magnification < 1: image reduced size.

To calculate magnification, measure the image size and actual size in the same units, then divide image size by actual size. For example, if an image is 10 cm and the actual object is 2 cm, magnification = 10 ÷ 2 = 5, meaning the image is 5 times larger.

• Measure image and actual size in same units.
• Divide image size by actual size.
• Interpret the result to understand image scale.

Magnification is calculated by dividing the size of the image by the actual size of the specimen: Magnification = Image size ÷ Actual size.

To find the actual size when magnification and image size are known, rearrange the formula: Actual size = Image size ÷ Magnification.

• Magnification = Image size ÷ Actual size.
• Actual size = Image size ÷ Magnification.
• Always use millimetres (mm) for measurements.

Use a ruler or scale bar to measure the image size on diagrams or microscope images. Convert all measurements to millimetres to maintain consistency and accuracy.

• Measure image size with a ruler in mm.
• Convert units to millimetres if needed.
• Use scale bars on images when available.

If an image of a specimen is 50 mm long and the magnification is 10, the actual size is calculated as 50 mm ÷ 10 = 5 mm. This method allows accurate determination of real specimen dimensions from magnified images.

• Calculate actual size by dividing image size by magnification.
• Use consistent units for reliable results.
• Apply this method to microscope observations and images.

Millimetres and micrometres are units used to measure length, especially in biology where small structures are measured.

1 millimetre (mm) equals 1000 micrometres (µm). This means micrometres are smaller units than millimetres.

• 1 mm = 1000 µm
• Micrometres are one-thousandth of a millimetre

To convert a measurement from millimetres to micrometres, multiply the number of millimetres by 1000.

This increases the value because micrometres are smaller units, so more micrometres fit into one millimetre.

• Multiply mm value by 1000 to get µm
• Example: 2 mm × 1000 = 2000 µm

To convert a measurement from micrometres to millimetres, divide the number of micrometres by 1000.

This decreases the value because millimetres are larger units than micrometres.

• Divide µm value by 1000 to get mm
• Example: 4500 µm ÷ 1000 = 4.5 mm