Sleep mode

Hi! I am completely new on Mac, but I love it, after 2 days I wander way I us Windows before, and to long time 25 years.

But I have some question abut iMac, (the white one)
1. When I put computer to sleep, it go back on when I turn the lamp off in the room or the next room.
2. How do I turn down the volume on start up, now I wake every one up if I want to use the Mac i early morning

Best Regards
Tommy

for #2

read end of http://www.mac-forums.com/forums/os...re-simple-way-lower-startup-chime-volume.html

I tray that one, but don't work on my system OSX 10.55
Do you know any thing about the sleeping problem?