GCSE · Biology · AQA · Spec 8461
Microscopy: light vs electron
The microscope you choose decides how much of the cell you can actually see.
What you need to know
- Electron microscopes have higher magnification AND higher resolving power (resolution) than light microscopes.
- Resolution is the ability to distinguish two points that are very close together as separate points — higher resolution reveals finer detail.
- Magnification is calculated using [[EQ:image_magnification]]; image size and real object size must be in the same units before calculating.
- Units used for cell sizes: millimetre (mm), micrometre (µm) and nanometre (nm) — be fluent converting between them.
The big picture
Microscopy techniques have developed over time, giving scientists increasingly detailed views of cells and sub-cellular structures. Light microscopes and electron microscopes differ in their magnification and resolving power, with electron microscopes able to reveal far finer detail. Magnification tells you how many times bigger the image is than the real object, calculated using [[EQ:image_magnification]]. Being fluent at converting between millimetres, micrometres and nanometres is essential when working with cell and image sizes.
TONIGHT'S REVISION
Microscopy: Light vs Electron
Magnification, resolution, and the maths behind measuring cells
Stop and think
Read carefully — these two terms are easy to mix up.
A scientist increases the magnification of their microscope from ×500 to ×2000, but the resolving power stays the same. What happens to the image of two very close-together points?
Using the magnification equation — step by step
Follow these steps every time — unit mismatches are the most common error.
Relationship matrix
Tap any cell to reveal it. Tap a column header to read one property down every item.
Each cell hides a short answer and the reason behind it. Predict before you tap.
LIGHTBULB PRACTICE
Practice questions
Does your answer hit all the marking points?
Question
Explain why the development of electron microscopes has increased our understanding of sub-cellular structures compared with light microscopes. [4 marks]
Student answer
Electron microscopes have a higher magnification than light microscopes. They also have a higher resolving power. This means they can distinguish two points that are very close together as separate points. As a result, sub-cellular structures can be seen in far greater detail.
Key points
Worked example
Problem
A student views a cell under a microscope. The image of the cell measures 24 mm. The actual cell is 0.04 mm wide. Calculate the magnification.
Memory hook
MR BIG: Magnification makes it Bigger; Resolution makes it clearer. You need both — but Resolution is the Real limit.
★ Exam tip
Write the equation with the numbers substituted in matching units before calculating — this is the step most likely to go wrong.
⚠ Watch out
Mixing units before dividing — e.g. putting image size in mm and real size in µm into [[EQ:image_magnification]] without converting. Always make both values the same unit first.
Check yourself
Without looking — what is the difference between magnification and resolution, and which one limits how much detail you can see in an image?
Flashcards
(26)What does magnification tell you?
Write the magnification equation using the placeholder.
What is resolution (resolving power)?
Which type of microscope has higher magnification?
Which type of microscope has higher resolving power?
What does higher resolution allow scientists to do?
How many micrometres are in 1 millimetre?
How many nanometres are in 1 micrometre?
Convert 0.005 mm into micrometres.
Convert 350 nm into micrometres.
An image measures 15 mm and the real object is 0.03 mm. What is the magnification?
Magnification = 200; image size = 40 mm. What is the real object size?
Magnification = 400; real object size = 0.05 mm. What is the image size?
What units does magnification have?
If magnification increases but resolution stays the same, what happens to the image of two very close-together points?
What has the development of electron microscopy allowed scientists to do?
Convert 2500 µm into mm.
Express 0.002 mm in standard form.
What is the unit prefix 'micro' equivalent to as a multiplier?
What is the unit prefix 'nano' equivalent to as a multiplier?
What is the unit prefix 'centi' equivalent to as a multiplier?
Before using [[EQ:image_magnification]], what must you always check?
A cell image is 36 mm and the magnification is 1200×. What is the real size of the cell in µm?
Convert 4500 nm into µm.
A real object is 8 µm. Its image is 40 mm. What is the magnification? (Convert image to µm first.)
Why do electron microscopes increase our understanding of sub-cellular structures?
Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.
Learn Microscopy: light vs electron properly — interactive practice, marked questions and flashcards.
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