log to the base 2

How many times can you divide N things in half?

    N/2/2/2/2/2/2/.../2 = a
     |_________________|
           k times

N * 2^(-k) = 1

N = 2^k

k = log₂(N)

How many accesses will it take to find X as we increase N ?

N	log2(N)
1	1
10	3
100	7
1000	10
1000000	20