How can independent assortment explain genetic diversity in humans? how many pairs of chromosomes are in a human diploid cell?

Independent assortment states that all alleles are inherited independently of other alleles. This helps diversity because it helps to further the randomization of traits. If traits were always inherited together, as a "package deal", there would naturally be less diversity than the situation that exists. For example, one may never see a person with blue eyes and brown hair if the alleles for the two traits, hair and eye color, were inherited together. However, it is worth noting that there is "genetic linkage", meaning full or partial violation of independent assortment among certain trait groups. 

There are 46 chromosome in a normal human diploid cell, 23 inherited from the mother's egg and 23 inherited from the father's sperm.