Using millimetres and micrometres as units

• The table below shows how millimetres are related to two other measures of length
• What this basically means is that 1mm = 1000μm and 1cm = 10,000μm
• This usually comes up in questions where you have two different units and you need to ensure that you convert them both into the same unit before proceeding with the calculation
• For example:

Example extended magnification question

• Remember 1mm = 1000μm
• 2000 / 1000 = 2 so the actual thickness of the leaf is 2mm and the drawing thickness is 50mm
• Magnification = image size / actual size = 50 / 2 = 25
• So the magnification is x 25 (NO UNITS)