IGCSE›Cambridge IGCSE Biology›Mind mapsSize of SpecimensCambridge IGCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsMagnificationHow many times larger the image is than the specimenmagnification=image sizeactual size\text{magnification} = \frac{\text{image size}}{\text{actual size}}magnification=actual sizeimage size×400 means image is 400 times biggerAlways write the × symbolRearrangingimage size=magnification×actual size\text{image size} = \text{magnification} \times \text{actual size}image size=magnification×actual sizeactual size=image sizemagnification\text{actual size} = \frac{\text{image size}}{\text{magnification}}actual size=magnificationimage sizeUse only the number (400) in the formulaActual size is much smaller than the imageSpecimen sizemagnification×mmμmUnitsImage usually measured in mm with a ruler1 mm=1000 μm1\,\text{mm} = 1000\,\mu\text{m}1mm=1000μmmm → μm: multiply by 1000μm → mm: divide by 1000Convert so both units match firstWorked exampleOnion cell image 12 mm at ×400actual=12÷400\text{actual} = 12 \div 400actual=12÷400= 0.03 mm= 30 μmExam tipsWrite formula, substitute, then answerAlways include unitsDivide for actual size, never multiplyShow working for method marks