condition one ring will not be equal to one year rather less than one year ,similarly if ring is thin(I know it indicates bad year i.e unfavorable conditions)does it mean rings are far apart ?then again one ring will not be equal to one year instead more than one year so how dendrochronology gives right age of the tree?one more question my textbook says one annual ring is equal to two rings one autumn wood (darketr in color)and one spring wood(lighter in color) ,so is it wrong? I have searched on Google everyone says one year =one ring not two

It is one year, not two. The reason being the change in seasons, say winter came early; spring late, etc.