# A-level Physics (Advancing Physics)/Digital Storage/Logarithms

That formula involved logarithms. If a^{b} = c, then:

In other words, a logarithm is a way of asking the question, "*a* to the power of what is *c*?" *a* is known as the base of the logarithm. log a is shorthand for log_{10}a, and can be calculated using the 'log' button on a scientific calculator.

Just as with indices, there are some laws of logarithms. At present, we are only concerned with this one:

If we apply this to the formula for calculating the number of possible values a pixel can take on (v = 2^{b}), we can rearrange it to get a formula for *b* by taking the logarithm to the base 10 of both sides:

We can then use a scientific calculator to calculate log 2, giving us the formula: