# 2.1.3 Measuring objects seen with a light microscope

### Description

AS level Biology (2.1- Cell Structure) Mind Map on 2.1.3 Measuring objects seen with a light microscope, created by Aleena Sheraz on 07/03/2017.
Mind Map by Aleena Sheraz, updated more than 1 year ago
 Created by Aleena Sheraz over 7 years ago
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## Resource summary

2.1.3 Measuring objects seen with a light microscope
1. Using graticules
1. Microscope eyepiece= fitted with graticule
1. Graticule= transparent with a small ruler etched on
1. The scale is arbitrary - represents diff. lengths at diff. magnifications
2. As a specimen is viewed the eyepiece graticule scale is superimposed and the dimensions of specimen can be measured in epu
1. Eyepiece scale has to be calibrated for each different objective lens by using a stage graticule
1. Stage graticule= precise measuring divide with a small scale to calibrate value of eyepiece divisions at different magnifications
3. Using a stage graticule to calibrate the eyepiece graticule
1. A stage graticule, microscopic ruler, is placed on the microscope stage
1. Ruler is 1mm long with 100 divisions= each division is 0.01mm or 10um
2. 1) Insert eyepiece graticule in X10 eyepiece of microscope
1. 2) Place a stage graticule on microscope stage, bring to focus, use low power X4 objective. T. magnification= X40
1. 3) Align eyepiece and stage graticule. Check value of 1 eyepiece division
1. 4) In the example, stage graticule (1000um) corresponds to 40 eyepiece divisions
1. 5) Each eyepiece division= 1000/40 = 25um
1. 6) Now use X10 objective lens (T. magnification is X100) and focus on stage graticule
1. 7) Align both graticules
1. 8) From the example, 100 eyepiece divisions correspond with 1000um
1. 9) So one eyepiece division= 1000/100= 10um

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