Final answer:
An age bar graph compares the relative number of individuals within different age groups of a population using rectangular bars of different heights or lengths.
Step-by-step explanation:
The graph that compares the relative number of individuals within different age groups of a population is called an age bar graph. Bar graphs represent data using rectangular bars of different heights or lengths, with each bar corresponding to a specific age group and the length of the bar indicating the relative number of individuals in that group. This type of graph allows for easy comparison of the population distribution across different age groups.