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Micrometry Technique Cheat Sheet

A Education › Biology cheat sheet in English by UmeshJagtap

To calibrate the Ocular Micrometer Scale and measure biological samples using the Micrometry Technique.

Beginner Lab Stage
6,461 views 1,127 downloads 25 Aug 2023 History
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AIM

Measur­ements using the Ocular Micrometer (Micro­metry Techni­que).

OBJECTIVES

1. Calibrate the Ocular Micrometer Scale.
2. Measure samples using the Ocular Micrometer Scale.

INTROD­UCTION

Micrometer scales within the ocular of a microscope are employed to determine sample sizes. These specia­lized oculars possess a transp­arent scale graticule superi­mposed onto the observed image. By replacing the stage micrometer with the sample slide, you can measure cell sizes. Micrometry is a crucial technique in biology, especially in micros­copy, using ocular and stage microm­eters to measure biological struct­ures.

1. OCULAR MICROMETER

Descri­ption:
Transp­arent ruler-like device without units, mounted on eyepiece.
Design:
Glass disc featuring 10 mm scale divided into 100 sub-di­vis­ions.
Visibi­lity:
Scale visible through microscope eyepiece.

2. STAGE MICROMETER

Placement:
Positioned on microscope stage.
Constr­uction:
Slide with 2 mm scale divided into 0.01 mm (10 µm) sub-di­vis­ions.
Function:
Used to calculate ocular micrometer divisions at specific magnif­ica­tions.

REQUIR­EMENTS

Compound light microscope with bjectives (4X, 10X, 20X, 40X),
Ocular micrometer scale
Stage micrometer (0.01 mm scale).
Microscope Glass slide
Coverslip

PROTOCOL

Part I: Calibr­ation of Ocular Micrometer
1. Place the ocular micrometer in the microscope eyepiece.
2. Adjust the lighting for optimal Kohler illumi­nation.
3. Focus on the stage micrometer using the lowest magnif­ica­tion.
4. Rotate to the objective designated for calibr­ation.
5.Adjust the focus of the ocular micrometer to visualize both scales clearly.
6. Align the stage and ocular scales with a slight offset for ease of reading.
7. Choose two positions on each scale, preferably on opposite sides.
8. Count the divisions on the stage scale (ssd) between the chosen positions.
9. Count the divisions on the ocular scale (osd), which equals ssd.
10. Record the number of ocular spaces (y) and stage spaces (x).
11.Cal­culate the calibr­ation factor: 1 ocular space = (x/y) × 10 µm.
12.Repeat the process for the second assigned objective.

Figure1:

Figure1:
Microscope Field of View Showing Ocular Micrometer and Stage Micrometer Superi­mposed each other.

Observ­ation Table 1: Calibr­ation of Objectives

Objective Power
Observ­ation No.
Ocular Divisions (Y)
Stage Divisions (X)
Calibr­ation Factor (X/Y × 10 µm)
Mean Calibr­ation factor
10X
1
 
2
 
3
40X
1
 
2
 
3

Part II: Protocol for Using Microm­eters

1. Place biological sample slide (e.g. Pollen Grain), focus on area.
2. Locate ocular micrometer through eyepiece.
3. Align structure with ocular microm­eter.
4. Count ocular divisions needed to span the structure.
5. Repeat for other objectives and other biological specimens.
6. Record divisions for each measur­ement.
7. Calculate structure size (e.g. pollen grain): Ocular divisions × calibr­ation factor.
8. This protocol accurately measures biological struct­ures.

Observ­ation Table2 :Measu­rement of Plant Samples

Plant Samples
Microscope Objective Power
Calibr­ation Factor (CF)
Observ­ation No.
Ocular Divisions (OSD)
Size of Sample (OSD × CF)
Mean Size (µm)
Pollen Grain
10X
  
1
     
2
     
3
 
40X
  
1
     
2
     
3

RESULTS

Size of Pollen Grain under 10X = _________ µm
Size of Pollen Grain under 40X = _________ µm

CONCLUSION

In conclu­sion, micrometer scales within microscope oculars are pivotal for accurate sample size determ­ination in biology. By replacing the stage micrometer with a sample slide, cell sizes can be measured

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