Describe how we breathe in.

A scientist prepared alveolar tissue to view using an optical microscope. The scientist cut very thin slices of the alveolar tissue.

Explain why the scientist used very thin slices of alveolar tissue with the optical microscope.

Figure 2 is an image of the lung tissue observed using an optical microscope.

Identify the tube labelled A.

A

The scientist used a ruler to measure the diameter of some of the alveoli.

Table 2 shows the scientist's results.

The magnification of the image in Figure 2 is × 40

Use this information and Table 2 to calculate the mean diameter, in μm, of the alveoli.

Show your working.

Answer ______________ μm

Give the uncertainty associated with taking a measurement using a ruler with 1 mm graduations.

Calculate the percentage error for a measurement using the ruler of 4 mm

Uncertainty ± ______________ mm

Percentage error