How to study cells - Microscopes, magnification and calibrating the eyepiece graticule

Summary

In this educational video, Mr. Ik explores the world of microscopes, focusing on their types, magnification, and calibration. He explains the difference between optical and electron microscopes, highlighting the latter's superior resolution and magnification for detailed cellular observation. The tutorial covers the magnification formula, unit conversion, and the calibration process of the eyepiece graticule using a stage micrometer. This comprehensive guide is aimed at students seeking to understand microscopes for their A-Level biology studies.

Takeaways

• 🔬 The video covers the topic of microscopes, focusing on magnification calculation, unit conversion, and calibration of the eyepiece graticule.
• 🌟 Mr. Ik discusses three key types of microscopes: optical or light microscopes, and two types of electron microscopes - transmission and scanning electron microscopes.
• 🔍 Magnification in microscopes refers to the size increase of the image compared to the actual object size, while resolution is the minimum distance between two objects that can still be viewed as separate.
• 🌈 Optical microscopes have lower resolution and magnification but allow for color images and the use of living samples.
• 🖤 Electron microscopes offer higher resolution and magnification but produce black and white images and require samples to be in a vacuum, thus not suitable for living samples.
• 📏 The formula for calculating magnification is image size equals actual size times magnification, which can be rearranged to find either value.
• 📐 Unit conversion is necessary when measuring image sizes in millimeters and actual sizes in micrometers, with millimeters converted to micrometers by multiplying by 1000.
• 📏 The eyepiece graticule is a tool for measuring the size of objects under the microscope, but it requires calibration using a stage micrometer.
• 🔧 Calibration of the eyepiece graticule involves aligning it with a stage micrometer, counting divisions, and calculating the value per division at different magnifications.
• 🔬 The video concludes with a summary of key points, including the differences between microscope types, the use of the magnification formula, and the importance of calibrating the eyepiece graticule.

Q & A

What are the three key types of microscopes mentioned in the script?

The three key types of microscopes mentioned are the optical or light microscope, and the electron microscopes, which include the transmission electron microscope and the scanning electron microscope.

What is the definition of magnification in the context of microscopes?

Magnification refers to how many times larger the image that you look at is compared to the actual size of the object.

What is the definition of resolution or resolving power in microscopy?

Resolution or resolving power is the minimum distance between two objects which they can still be viewed as separate, meaning they do not blur into looking like one single point.

Why do electron microscopes have a higher resolving power and magnification than optical microscopes?

Electron microscopes have a higher resolving power and magnification because electrons have a much shorter wavelength than light, which allows for higher detail and magnification in the images they produce.

What is the difference between a transmission electron microscope and a scanning electron microscope?

A transmission electron microscope passes a beam of electrons through a very thin specimen, creating a 2D image with varying shades of white and black based on electron absorption. A scanning electron microscope, on the other hand, scatters and reflects electrons off the surface of the specimen, creating a 3D image that provides details on texture and depth.

Why can't living samples be viewed with an electron microscope?

Living samples cannot be viewed with an electron microscope because the electron beam would be absorbed by air, and the samples need to be in a vacuum for the electrons to reach and interact with the specimen to create an image.

What is the formula used to calculate magnification from a microscope image?

The formula used to calculate magnification from a microscope image is Image Size (I) = Actual Size (A) × Magnification (M).

How do you convert millimeters to micrometers when measuring a microscope image?

To convert millimeters to micrometers, you multiply the number of millimeters by a thousand, since one millimeter is equal to one thousand micrometers.

What is an eyepiece graticule and why is it necessary to calibrate it?

An eyepiece graticule is a glass disk with a scale etched onto it, located within the eyepiece of a microscope. It is necessary to calibrate it because the value of each division on the graticule changes with different magnifications, and calibration ensures accurate measurements of the specimen.

How do you calibrate an eyepiece graticule using a stage micrometer?

To calibrate an eyepiece graticule, you place a stage micrometer on the microscope stage and align it with the eyepiece graticule. You then count how many divisions on the eyepiece graticule fit into one division on the stage micrometer, and use the known value of the stage micrometer's divisions to determine the value of each division on the eyepiece graticule at the current magnification.