How It Works: Light vs Electron Microscopes
Part of Microscopy — GCSE Biology
This how it works covers How It Works: Light vs Electron Microscopes within Microscopy for GCSE Biology. Light and electron microscopes, magnification and resolution calculations, specimen preparation, staining techniques, and practical microscopy skills It is section 12 of 19 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 12 of 19
Practice
18 questions
Recall
20 flashcards
How It Works: Light vs Electron Microscopes
Light Microscopes — How They Form an Image
A light microscope uses visible light and a series of glass lenses to produce a magnified image. Light from a bulb passes through a condenser lens that focuses it onto the specimen. The objective lens (close to the specimen) bends the light rays to create a real, magnified image. The eyepiece lens then acts like a magnifying glass, enlarging this intermediate image further before it reaches your eye. The total magnification is the product of both lenses: eyepiece (usually x10) multiplied by the objective (x4 to x100).
Why Magnification and Resolution Are Different
Magnification is simply how many times larger the image appears compared to the real object. Resolution is the ability to distinguish two points that are very close together as separate — it determines sharpness. A light microscope is limited in resolution by the wavelength of visible light (around 400-700 nm). Two structures closer than about 200 nm will always appear blurred into one, no matter how much you magnify the image. This is why simply increasing magnification without improving resolution produces a larger but blurry image — known as empty magnification.
Electron Microscopes — Why They Give Better Resolution
Electron microscopes use beams of electrons instead of light. Electrons have a much shorter wavelength than visible light, which allows them to resolve structures as small as 0.05 nm. This is why organelles like ribosomes (about 20 nm) and the double membrane of mitochondria can only be seen with an electron microscope — they are far below the resolution limit of a light microscope. The trade-off is that specimens must be prepared in a vacuum and cannot be alive.
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