Eyepiece graticule and stage micrometer A level Biology - BioTeach

Bio Teach

22 Sept 202005:15

Summary

TLDRThis video from BioTeach explains how to calibrate microscopes using an eyepiece graticule, a tool crucial for A-Level biology students studying cells. The graticule, placed in the eyepiece, is calibrated against a stage micrometer to measure objects under the microscope. The tutorial walks through aligning the graticule with the stage micrometer, calculating the size of each division, and applying this calibration to measure cell sizes accurately. The video is a practical guide for lab practice, emphasizing the need for recalibration with different magnifications or microscopes.

Takeaways

🔬 The video focuses on how to calibrate microscopes using the eyepiece graticule, essential for A-Level biology students.
📏 The eyepiece graticule is used to measure the size of objects under a microscope and is typically 1 millimeter long, divided into 100 units.
🧪 A stage micrometer, also 1 millimeter long and divided into 100 divisions, is used to calibrate the eyepiece graticule.
🔧 To calibrate the microscope, the eyepiece graticule must be aligned with the stage micrometer.
📊 Once aligned, the number of divisions on the eyepiece graticule that correspond to stage micrometer divisions must be counted.
📐 The video explains a calculation where 10 stage micrometer divisions correspond to 21 eyepiece graticule divisions.
🎯 The size of each division on the eyepiece graticule can be calculated by dividing the micrometer measurement by the number of divisions.
🧬 After calibration, measurements in micrometers can be made on the sample, such as determining the size of cheek cells.
🔄 The eyepiece graticule must be recalibrated for each magnification or when using a different microscope.
📚 The video teases an upcoming comparison of optical and electron microscopes, including past exam questions.

Q & A

What is the main topic of the video?
-The main topic of the video is how to calibrate microscopes using the eyepiece graticule, which is relevant for A-level biology students studying cells.
What is a graticule used for in microscopy?
-A graticule is used to measure the size of an object viewed under a microscope. It is placed in the eyepiece of the microscope and is often about one millimeter long, divided into 100 equal units.
What is the purpose of a stage micrometer in microscopy?
-A stage micrometer is a slide with a scale that is exactly one millimeter long, divided into 100 divisions. It is used in combination with a graticule to calibrate the microscope so that a precise scale can be calculated at each magnification.
How does the calibration process of the eyepiece graticule work?
-The calibration process involves aligning the eyepiece graticule with the stage micrometer, counting how many divisions on the graticule correspond to a set of stage micrometer divisions, and then calculating the size of one division on the graticule based on the known size of the stage micrometer divisions.
Why is it necessary to recalibrate the eyepiece graticule for different magnifications?
-It is necessary to recalibrate the eyepiece graticule for different magnifications because the scale of the graticule changes with the magnification, and the calibration ensures accurate measurements of the specimen.
What is the significance of the 100 divisions on the stage micrometer?
-The 100 divisions on the stage micrometer are significant because each division represents 0.01 millimeters, allowing for precise measurement when calibrated with the eyepiece graticule.
How can you remind yourself of the alignment between the eyepiece graticule and the stage micrometer while looking through the microscope?
-You can rotate the eyepiece slightly to remind yourself of the alignment between the eyepiece graticule and the stage micrometer, as it can be confusing to remember which is which when looking through the microscope.
What is the conversion factor from millimeters to micrometers?
-The conversion factor from millimeters to micrometers is 1000, as 1 millimeter is equal to 1000 micrometers.
What is the importance of knowing the magnification when measuring cells under a microscope?
-Knowing the magnification is important because it allows you to convert the number of divisions counted on the eyepiece graticule into an actual length, providing accurate measurements of the specimen.
Why is it necessary to recalibrate the eyepiece graticule when using a different microscope?
-It is necessary to recalibrate the eyepiece graticule when using a different microscope because the magnification and scale may vary between microscopes, and recalibration ensures accurate measurements.
What is the next topic that will be covered in the series of videos?
-The next video will be based on the types of microscopes, comparing optical microscopes to electron microscopes, and it will also cover some past paper questions related to microscopy.

Outlines

00:00

🔬 Microscope Calibration Using Eyepiece Graticule

This video by Bioteach educates viewers on the calibration of microscopes using an eyepiece graticule, a vital skill for A-level biology students studying cells. The graticule, placed in the microscope's eyepiece, is typically one millimeter long and divided into 100 units. It is used in conjunction with a stage micrometer, a slide with a precise one-millimeter scale, to measure the size of objects under the microscope. The video demonstrates the calibration process, which involves aligning the graticule with the stage micrometer and calculating the size of each graticule division based on the stage micrometer's divisions. The example provided shows that 10 divisions on the stage micrometer correspond to 21 divisions on the eyepiece graticule, leading to the calculation that one division on the eyepiece graticule is 4.8 micrometers. The video emphasizes the necessity of recalibrating the graticule for each microscope and magnification used, ensuring accurate cell measurements.

05:00

👋 Acknowledgment of Viewer

The second paragraph is a brief acknowledgment of the viewer, likely a direct address to the audience, possibly indicating a transition or a pause in the video. The content is minimal, consisting only of the word 'you,' suggesting a personal touch or a moment of engagement with the viewers.

Mindmap

Keywords

💡Eyepiece Graticule

An eyepiece graticule is a small scale placed in the eyepiece of a microscope used to measure the size of objects. It is typically 1 millimeter long and divided into 100 equal units. In the video, it is essential for calibrating the microscope and measuring objects like cells.

💡Stage Micrometer

A stage micrometer is a microscope slide with a precise scale, 1 millimeter long, also divided into 100 divisions. It is placed on the microscope stage to calibrate the eyepiece graticule. The stage micrometer allows users to determine the actual size of objects viewed under the microscope by comparing its known scale to the eyepiece graticule divisions.

💡Calibration

Calibration is the process of adjusting the microscope's eyepiece graticule to match a known scale, such as that of the stage micrometer. In the video, calibration ensures accurate measurements at each magnification level. It involves aligning the scales of the eyepiece graticule and stage micrometer and calculating the size of divisions.

💡Magnification

Magnification refers to the microscope's ability to enlarge an object’s image. In the context of the video, calibration must be performed for each magnification level because the size of the graticule divisions changes with magnification. Without recalibration, measurements would be inaccurate.

💡Micrometers

A micrometer (μm) is a unit of length equal to one-millionth of a meter. It is used to measure small objects like cells. In the video, measurements from the microscope are converted from millimeters to micrometers to make it easier to work with smaller, more practical numbers, such as when calculating the size of cheek cells.

💡Hemocytometer

A hemocytometer is a specialized microscope slide used to count cells. Although the video focuses on the eyepiece graticule, it briefly mentions the hemocytometer as another tool for measuring and counting objects under a microscope. The hemocytometer is more commonly used in biological studies for counting blood cells or other small particles.

💡Division

A division is a marked unit on the eyepiece graticule or stage micrometer. The eyepiece graticule has 100 divisions, each representing an equal fraction of a millimeter. By aligning the eyepiece graticule with the stage micrometer, the number of divisions can be calculated to determine the actual size of an object. For example, 10 micrometer divisions equal 21 eyepiece divisions.

💡Cheek Cells

Cheek cells are used as an example in the video to demonstrate how to measure objects under a microscope. After calibrating the eyepiece graticule, the length of a cheek cell is measured to be 16 graticule units, which is calculated to be approximately 76.8 micrometers in length.

💡Optical Microscope

An optical microscope uses light to magnify images of small objects. In the video, the calibration process and usage of eyepiece graticules are demonstrated with an optical microscope. The upcoming video mentioned will compare optical microscopes with electron microscopes.

💡Cells

Cells are the basic structural units of life and are frequently observed under microscopes in biology. The video explains how to measure cells using an eyepiece graticule after calibration. For example, cheek cells are measured to determine their length in micrometers.

Highlights

Introduction to calibrating microscopes using the eyepiece graticule for A-level biology students.

Explanation of the necessity of precise measuring equipment for microscopic observations.

Description of the graticule and its placement in the eyepiece of a microscope.

Introduction to the stage micrometer and its role in calibrating the graticule.

Demonstration of aligning the eyepiece graticule with the stage micrometer.

Instruction on counting divisions on the graticule corresponding to stage micrometer divisions.

Guidance on identifying the scale of the stage micrometer for calibration purposes.

Calculation of the size of one division on the eyepiece graticule.

Conversion of measurements from millimeters to micrometers for practical use.

Procedure for measuring a specimen using the calibrated eyepiece graticule.

Example calculation of the size of a cheek cell using the calibrated graticule.

Emphasis on recalibrating the graticule for each microscope and magnification used.

Upcoming video teaser on types of microscopes and comparison with electron microscopes.

Encouragement for viewers to ask questions in the comments section for further clarification.

Conclusion and sign-off, thanking viewers for watching the video.