I am having large number of visitors but less adsense income

It is hard to offer any suggestions without any figures.

But if it has just been a day or two that this has occurred, I would wait a week to see if the earnings do not rise proportionally. The Adsense guys do seem to withhold earnings for a few days and then release it to your account a few days later.

It could be the fact that it is the end of the month and advertisers in your niche have depleted their advertising budgets. This would of course mean less earnings per click for guys like you.

It could be that the source of your increase in traffic is supplying you with poor quality traffic. I remember I was once suddenly getting 1000% boost to the traffic to a site. My income remained the same. Further investigation revealed that the all of the new traffic was from some traffic exchange program. Even though I never joined the program, I was somehow getting tons of traffic from it.

Smart pricing also comes to mind amongst other things.

My suggestion is wait a few days to see if the changes are not just temporary and also try to use statcounter.com or some other web statistics package to help you track your traffic sources.