Consider a transistor in common base configuration biased in active region of operation. As you increase collector to base voltage that is if you more reverse bias base collector junction the depletion layer width increases as depletion layer width is proportional to reverse bias voltage. This depletion layer protrudes more in to the base than collector because base is lightly doped compared to collector. As we increase base to collector voltage depletion layer width increases this in turn decreases effective base width. According to law of junction injected carrier concentration in base should reduce to zero at the onset of depletion layer in base. In the graph(plotted with minority carrier concentration on Y-axis anddistance from emitter base junction to base collector junction on x-axis stands) shown below the left side is plotted for higher reverse bias compared to graph on right side with less slope compared to the one on the right .This is termed as Early effect.