Eyepiece graticule and stage micrometer A level Biology - BioTeach

Summary

This 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.