For a microscope that uses light, what measures the size of objects?
An eyepiece graticule, this is a glass disc that is placed in the eyepiece of a microscope. There is a scale etched on the glass disc.
Why must the eyepiece be calibrated?
To ensure the scale stays accurate.
How do you calibrate an eye piece?
you need to use a special microscope slide called a stage micrometer, this slide also has a scale etched onto it.