Microscopy - How to use a microscope - GCSE Science Required Practical

Summary

This educational video script offers a comprehensive guide on using a microscope for biological experiments. It covers the microscope's parts, proper setup, and use, including adjusting the light source and mirror for optimal illumination. The script instructs viewers on preparing a specimen slide with onion skin, staining it with iodine, and focusing under the microscope. It also explains how to change magnification levels and provides a method for estimating cell size by measuring the field of view and calculating the width of cells in microns, which is crucial for recording observations in a practical biology setting.

Takeaways

• 🔬 The microscope is a crucial tool in biological experiments, essential for observing small samples like onion skin cells.
• 💡 Proper setup of the microscope involves adjusting the light source and mirror to ensure optimal illumination of the specimen.
• 🔍 The microscope's magnification is controlled by the objective lenses, with options ranging from 4x to 40x, combined with a 10x eyepiece for total magnifications of 40x to 400x.
• 📏 Preparing a specimen involves placing a thin layer of onion skin on a glass slide, adding iodine to stain the cells, and covering it with a cover slip to prevent creasing and ensure clear viewing.
• 👁️‍🗨️ Focusing on the specimen requires starting with the lowest magnification and gradually adjusting the coarse and fine focus knobs until the cells come into clear view.
• 🔄 Changing magnification involves rotating the turret to switch objective lenses and making slight adjustments to maintain focus.
• 📐 Measuring cell size involves aligning cells across the field of view, using a transparent ruler to measure the field of view's width, and calculating the size of individual cells based on the number of cells spanning the view.
• 📝 Accurate cell measurements are expressed in micrometers (µm), with 1000 µm equal to 1 millimeter, and are crucial for scientific records and understanding cell dimensions.
• 🎨 Making microscope drawings is an important skill, requiring sharp pencils and accurate representation of cell structures observed under the microscope.
• 🔋 The process of using a microscope includes troubleshooting tips for focusing issues, such as ensuring the lowest magnification is used first and adjusting the focus slowly and carefully.

Q & A

What is the primary purpose of using a microscope in biological experiments?

The primary purpose of using a microscope in biological experiments is to observe and analyze samples at a high magnification, allowing for the study of cellular structures and other minute details that are not visible to the naked eye.

What is the first step in setting up a microscope for use?

The first step in setting up a microscope for use is to adjust the mirror and light source to ensure that adequate light is reflected up through the stage, creating a bright field of view for observing the specimen.

Why is it important to start with the lowest magnification lens when using a microscope?

Starting with the lowest magnification lens is important because it provides a wider field of view, making it easier to locate and center the specimen before switching to higher magnifications for more detailed observation.

What is the function of the mirror in a microscope setup?

The mirror in a microscope setup is used to reflect light from the light source up through the stage and onto the specimen, ensuring that the specimen is well-illuminated for clear viewing.

How should you handle glass slides when preparing a specimen for microscopy?

When handling glass slides for microscopy, you should carry them by touching the edges only to avoid leaving greasy fingerprints on the glass surface, which could obscure the view of the specimen.

Why is iodine added to the onion skin sample before placing a cover slip?

Iodine is added to the onion skin sample to stain the starch within the cells, enhancing their visibility under the microscope by providing contrast against the cell walls.

What is the purpose of using a cover slip when preparing a microscope slide?

A cover slip is used to protect the specimen from contamination and damage, and it helps to keep the sample flat and in focus. It also prevents the sample from drying out and allows for better light transmission.

How can you avoid damaging the lens when changing the objective lens on a microscope?

To avoid damaging the lens when changing the objective lens, ensure that the new lens does not touch the slide by getting low and checking for clearance, and then carefully rotate the new lens into position without applying too much pressure.

What is the recommended method for focusing on a specimen at high magnification?

When focusing on a specimen at high magnification, it is recommended to first focus at a lower magnification, then switch to the higher magnification lens, and make only minor adjustments to the fine focus to bring the specimen into sharp view.

How can you estimate the size of cells under a microscope?

To estimate the size of cells under a microscope, you can measure the distance spanned by a known number of cells in the field of view using a transparent ruler, and then calculate the average size of each cell based on the total distance and the number of cells.