One of the fundamental goals of a lab experience is finding the law linking two quantities: you measure pairs of values , plot them, recognise the shape of the curve, and look for a mathematical model. When the relationship is linear everything is simple: the best-fit line directly gives the slope and intercept. But if the data follow a curve — an exponential, a power law — there is a powerful trick: linearising via the logarithm. The two main tools are the semilogarithmic graph (for exponentials) and the bilogarithmic graph (for power laws).