Calculate the magnification given the length of a diagram and the length of the object it represents.

The formula for magnification is given as:

$$\text{Magnification} = \frac{\text{length of the diagram}}{\text{length of the object}}$$

From the question:
Length of the diagram = $8 \text{ cm}$
Length of the object = $2 \text{ cm}$

$$\text{Magnification} = 4$$

Magnification is a ratio and is typically expressed as a number followed by 'x'.

The magnification is:

$$\text{Magnification} = 4\text{x}$$