How do I work out the magnification of an image?

For these types of questions, start by writing out the equation for magnification: Magnification = (size of image) / (size of real object). Then, find the values given in the question that can be plugged into the equation. Often, the question provides the size of the real object, but you are expected to measure the size of the image yourself. Measure the image with a ruler in millimetres. This measurement needs converting into the units of the length of the real object. To convert millimetres into micrometres, simply multiply your measurement by 1000. Now, refer back to the equation for magnification. You now know the size of the image and the size of the real object. By dividing the size of the image by the size of the real object, you can work out the magnification. Top tip: Be careful with the units! Make sure that, before you divide, both measurements are in the same units- in this case this is micrometres.