Measuring cell size

• Graticule

  • a glass or plastic disc fitted into the eyepiece of a microscope
  • has a scale ruled on it
  • used to estimate the size of a specimen when viewed with a microscope
• • you must find out the distance measured for each division of the graticule
  • then use the graticule to measure cells
  • the distance will be different for each objective
• Stage micrometer

  • a glass slide with a scale etched on it
  • used to calibrate the eyepiece graticule of a microscope
• Calibrate

  • to set an instrument or scale against a standard
• 1. place a stage micrometer on the stage of the microscope
  2. line up one of the divisions on the eyepiece graticule with a fixed point on the stage micrometer
  3. count the number of divisions on the eyepiece graticule that correspond with a set measurement on the stage micrometer
  4. calculate the distance in micrometres of one division on the eyepiece graticule