Final answer:
To calculate magnification with a scale bar, measure the length of the scale bar on the image and divide it by the length of the actual scale bar.
Step-by-step explanation:
To calculate magnification with a scale bar, you need to first measure the length of the scale bar on the image of the object you are observing using the microscope. Then, divide the length of the scale bar on the image by the length of the actual scale bar. The result will give you the magnification of the microscope.
For example, if the length of the scale bar on the image is 1 cm and the actual length of the scale bar is 0.1 cm, the magnification would be 10x.