State and use the formula: magnification = image size ÷ actual size.

2.2 Size of Specimens

Objective

State and use the formula: magnification = image size ÷ actual size. 📐 Think of it as comparing a tiny insect on a microscope slide to the same insect in real life.

Key Formula

The magnification (M) is calculated as:
$M = \dfrac{I}{A}$
Where:

• $I$ = image size (measured on the slide or in the picture)
• $A$ = actual size (real-world size of the specimen)

Analogy: The Map Example

Imagine a city map where 1 cm on the map represents 1 km in real life. If a road on the map is 2 cm long, the real road is 2 km. Here, the “magnification” is 1 cm : 1 km, or 1 : 1000. The same idea applies to microscopes: the image on the slide is a “scaled-up” version of the tiny specimen.

Step‑by‑Step Example

1. Measure the actual size of a leaf: 5 mm.
2. Place the leaf on the microscope slide and capture an image.
3. Measure the image size on the slide: 25 mm.
4. Apply the formula:
   $M = \dfrac{25\,\text{mm}}{5\,\text{mm}} = 5$
5. Interpretation: The leaf appears 5 times larger in the image than it is in reality.

Practice Problems

Quick Check

If a microscope image shows a cell that is 15 mm long and the real cell is 3 mm, what is the magnification?
$M = \dfrac{15}{3} = 5$ The cell appears 5 times larger in the image. ??

Take‑away

Magnification tells us how many times bigger the image is compared to the real specimen. By remembering the simple ratio $M = I/A$, you can quickly calculate and interpret magnification in any microscopy experiment. Keep practicing with different specimens and you’ll become a magnification master! 🚀