why do we say that richter scale is not a linear scale ??? plzz if u know tell me fast ..!!

This is because the next value on the scale after the previous value does not increase in a linear order - like 1,2,3,4.. or 5,10, 15, 20. In the richter scale the magnitude of next value is 10 times the previous value, like 1, 10, 100, 1000...