Estimation of Cell Size.
The light microscope can be used to estimate the size of a cell. Most cells have diameters smaller than a millimeter. Due to this, cell sizes are always measured in smaller units. These are micrometres and nanometers. These units of measurements are related as shown below.
I millimeter (mm) = 1000 micrometres (μm).
I micrometer (μm) = 1000 nanometres (nm).
Procedure in cell size estimation
Using the low power objective, a transparent ruler is placed on the stage of the microscope.
An estimation of the diameter of the field of view is made in millimeters.
This is converted into micrometres (1mm=1000μm)
A prepared slide of onion epidermal cells is mounted.
The cells across the centre of the field of view are counted from left and right and top to bottom.
The diameter of field of view is divided by the number of cells lying lengthwise to give an estimate of the length and width of each cell.