Seeing beyond unaided eyesight

By UK GCSE Biology · independent study · myAudience

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Seeing beyond unaided eyesight

Magnification compares image size with actual size. Use magnification = image size ÷ actual size, with both sizes expressed in the same unit. Resolution is the ability to distinguish nearby details; enlarging a blurred picture does not create additional detail.

For a calculation, convert image size and actual size to the same unit before dividing. An image length of 12 mm is 12,000 µm; if the cell is 30 µm long, magnification is 12,000/30 = 400. A magnification has no length unit. An image displayed at a different size may need a scale bar rather than its original magnification label.

A light microscope forms an image using visible light; electron imaging can distinguish much finer features. Compare resolving power as well as magnification when deciding which image answers a question. When an image is resized on a screen, its printed magnification changes; a scale bar resized with the image remains useful because both lengths change in the same proportion.

Worked example: A cell is 20 µm across and its image is 10 mm across. Find magnification.

Convert 10 mm to 10000 µm

Divide 10000 by 20

Answer: Magnification is × 500.

Check your understanding: Would digital enlargement necessarily improve resolution?

Answer: No.

Why: It enlarges existing pixels without revealing structures that were not resolved originally.