Biology AS · Cell structure. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Magnification is how many times larger an image is than the real object. Resolution is the smallest distance between two points that can still be seen as separate. Making an image bigger does not add detail. Only better resolution does that.
A light microscope resolves about 200 nm, a limit set by the wavelength of light. A beam of electrons has a much shorter wavelength, so a transmission electron microscope resolves about 0.5 nm and shows ribosomes and membranes. A scanning electron microscope shows surfaces in 3-D.
To measure a cell, the eyepiece graticule is calibrated against a stage micrometer for each objective lens. Put image size and actual size in the same unit before you calculate.
Dividing a length in mm by a length in µm without converting. Change the image size to µm first (× 1000), then divide.
Answer: The chloroplast is 5 µm long.
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Cells as the basic units of living organisms →Take a Biology AS test