Microscopy: Magnification, Resolution & Types of Microscopes | A-level Biology | OCR, AQA, Edexcel

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The key points covered of this video include:

1. Principles of Microscopy
2. Magnification and Resolution
3. The Light Microscope
4. Laser Scanning Microscopes

Principles of Microscopy

The human eye can distinguish objects about 0.1mm apart - about the size of a human egg cell. Biologists want to study objects much smaller than this though, like bacteria and red blood cells. Eyes have limited magnification and resolution. To observe biology we need to increase our maximum magnification and resolution. We do this by using a microscope.

Magnification and Resolution

Different microscopes have different magnification and resolution. Magnification describes how many times bigger an image gets when it is put under the microscope. More powerful microscopes have higher magnification. Magnification is different from resolution. Resolution describes how much fine detail we can see in the image. It is defined as the smallest distance that two objects can be apart while still appearing as two objects. Here is a summary of magnification and resolution:

Light Microscope

Light microscopes were the first and still most common type of microscope. Light is sent from a light source through a specimen, the image of which is magnified by glass lenses. They are the most common because they are cheap, they are easy to use, they can be used to study living cells (which isn’t the case for all microscopes), Light microscopes show a 2D image of living cells, Light microscopes use visible light to create an image and this limits their resolution to 200nm and magnification to x2000.

Laser Scanning Microscopes

Laser scanning microscopes use a high power beam of light to create an image. The laser passes over each point in the specimen and creates an image over time. Laser scanning microscopes are more expensive than light microscopes but have a high resolution. They can also show specimens in 3 dimensions.

Summary
Magnification describes how many times larger an image appears
Resolution describes the smallest distance between two distinguishable points. Laser scanning microscopes have a higher resolution than light microscopes and can represent 3D specimens
Light microscopes magnify images using lenses
Light microscopes are cheap, easy to use, and can study living cells
They have a resolution of 200nm and a magnification of 2000x
Laser scanning microscopes have a higher resolution than light microscopes and can represent 3D specimens