GCSE Biology - Year 1 Week 2 - Microscopes
- Sallyann Clark
- Sep 29
- 4 min read
“How can something smaller than the width of a human hair be seen in incredible detail?”
Introduction
This week, you will explore how scientists can study cells in detail using microscopes. You’ll discover the differences between light microscopes, which use lenses and visible light, and electron microscopes, which use beams of electrons to reveal far greater detail. You will also learn how to use the magnification formula to calculate the actual size of tiny structures, and why improvements in microscope technology have been so important for advancing our understanding of biology. By the end of the week, you should be able to compare light and electron microscopes, use the magnification formula confidently, and explain how microscopes have shaped scientific discovery.
🔍 What am I learning today?
I can describe how light and electron microscopes work.
I can explain how scientific discoveries in microscopy improved our understanding of cells.
I can calculate magnification using the formula:
Magnification = Image size
Actual size
🧠 What should I already know?
From last week, you should remember:
Cells are the basic building blocks of life.
Eukaryotic and prokaryotic cells have different structures.
Watch Amoeba Sisters - Introduction to the Cell.
📘 Learning
1. Why do we use microscopes?
Cells are too small to see with the naked eye. Microscopes let us magnify them so we can explore their structures.
Light microscopes use visible light and glass lenses. They are cheap and easy to use, but cannot magnify as much.
Electron microscopes use beams of electrons and magnets instead of lenses. They produce much higher magnification and resolution, revealing details inside organelles.
📌 Board notes:
All boards require light vs electron microscope comparison.
🔺 Higher Tier (all boards): definition of resolution.
Resolution is the ability to distinguish two points separately.
📌 OCR only: more emphasis on differences in resolution values (light ≈ 200 nm, electron ≈ 0.1 nm).
2. The Magnification Formula
To calculate how much bigger an image is than the real object:
Magnification = Image size
Actual size
Image size is how big the picture looks (measured in mm).
Actual size is the true size of the object (often µm).
Use the triangle to help you rearrange the formula.
If you want to work out, cover I. You are left with A and M side by side, which means multiple. So, to find I multiple A and M.
If you want to find A, cover A. I is over M, so divide I by M.
Conversions to remember:
1 mm = 1000 µm (micrometres)
1 µm = 1000 nm (nanometres)
📌 Board notes:
All boards include the formula.
🔺 Higher Tier (all boards): rearranging the formula to calculate actual size.
Watch Cognito - What is Microscopy? and What is the Difference Between Light and Electron Microscopes?
Go and explore the ncbionetwork website.
The Story of the Microscope
A long time ago, in the 1500s, people knew about sickness, bugs, and plants, but they had no idea that tiny invisible worlds existed. They thought what they saw with their eyes was all there was.
👓 The First Lens-Makers (1500s, Holland)
Two Dutch spectacle makers, Hans and Zacharias Janssen, were playing around with glass lenses.One day, by accident, they put two lenses in a tube and looked through it.
“Whoa!” they shouted. “That fly’s eye looks HUGE!”
They had made the first compound microscope, though it was a bit blurry and weak.
Can you imagine looking through he compound microscope and seeing a giant flea?
🦠 The Curious Shopkeeper (1600s)
Fast forward to Antonie van Leeuwenhoek, a Dutch cloth seller. He loved making his own tiny, powerful lenses. His microscopes were small, like a magnifying glass on a stand, but super sharp. He peered at a drop of pond water and gasped:
“Look! Tiny animalcules!” (We call them microorganisms.)
He was the first human to see bacteria and protozoa, and he wrote to the Royal Society in London about his amazing discoveries.
The miniature world had become visible!
📚 The Careful Scientist (1665, England)
Meanwhile, in England, Robert Hooke was using his own compound microscope. He sliced up a cork and looked inside.
“It’s like tiny little rooms… I’ll call them cells!”
And so the word cell was born. Hooke’s book, Micrographia, had beautiful drawings that amazed London society. People queued up just to see the pictures.
The tiny rooms looked like monk cells, the rooms monks slept in, and that is why he named them cells.
🔬 Improving the View (1700s–1800s)
The microscopes kept improving:
Better glass
Better lighting
Stronger magnification
Now scientists could see cell walls, nuclei, and blood cells clearly.
💡 The Big Leap (1900s)
By the 20th century, scientists wanted to see even smaller things, tinier than light waves could show. Enter the electron microscope (1931), invented by Ernst Ruska.
Instead of light, it used beams of electrons. Suddenly, the invisible became visible:
Viruses
Cell organelles in detail
Even the structure of DNA
🏆 Today’s Microscopes
Light microscopes: in classrooms, good for cells and tissues
Electron microscopes: in research labs, good for tiny structures inside cells
Scanning electron microscopes: make 3D images of surfaces
Now, scientists can zoom in on the building blocks of life — all thanks to a few curious lens makers.
Watch TED-Ed - The Wacky History of Cell Theory.
If you want to know more about the history of the microscope, try the Science Museum Article.
Tasks
Label the microscope.
Create a timeline for the history of the microscope.
Record the three principles of Cell Theory in your journal.
Conclusion
This week you learned:
Light microscopes let us see basic cell structures, but electron microscopes give much greater detail.
The magnification formula helps us calculate real cell sizes.
Advances in microscopy have transformed how scientists understand cells.
🔮 Next week: we’ll explore how cells divide in the cell cycle and mitosis, and why stem cells are so important.
