A level Biology exam revision resources written by A level Examiners


As cells are so small, enlarged images are often required, in order to study them. Magnification is simply a measure of how much larger an image appears, than it's original size in real life. With most light microscopes the level of magnification is determined by the lens used.

Using more and more powerful lenses can increase magnification, with no theoretical limit, but there is a limit to how useful this will be. Imagine an image that appears blurred, and no detail can therefore be seen. If this image were increased in size, magnified in other words, by ten times, the image would remain blurry with no further detail visible. Resolution is the property that allows more detail to be seen.

original image
increased magnification
increased resolution

Resolution is the ability to distinguish between two points on an image.    Exam Advice

  • The resolution of an image is limited by the wavelength of radiation used to view the sample. The shorter the wavelength the greater the resolution.
  • The wavelength of light is much larger than the wavelength of electrons, hence the resolution of the light microscope is far lower than the resolution of an electron microscope.

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