Biology 9700/12 — October/November 2010

Which steps are needed to find the actual width of a xylem vessel viewed in transverse section using a $\times 40$ objective lens?

1 Convert from $\text{mm}$ to $\text{µm}$ by multiplying by $10^{-3}$.
2 Calibrate the eyepiece graticule using a stage micrometer on $\times 10$ objective lens.
3 Measure the width of the xylem vessel using an eyepiece graticule.
4 Multiply the number of eyepiece graticule units by the calibration of the eyepiece graticule.

Options

A   1, 2, 3 and 4
B   2, 3 and 4 only
C   1 and 2 only
D   3 and 4 only