Thanks for your effort but please take effort one more time for me. I have edited my question including one more question as you said to use $wf$ negative but in the another similar question using +ve value gives me right answer there. Please read the question.

I have done that only in my last equation, taking Initial P.E= mgH, final P.E=mgh and final heat energy=Wf. Hence $mgH=mgh+Wf$ which gave me wrong answer for Wf.

I just want to know that if you have been given all numerical values of all variables in the equation (ii). Example value of each variable in equation (ii) is 1 and you are asked to find out intensity of wave at a distance of 5m from the source using equation (ii) then how will you find it.

from your conclusion, $Sm=S0/r^2$, i.e. we can say that amplitude Sm is inversely proportional to square of distance from source. but we know intensity (I) is directly proportional to square of amplitude ($Sm^2$) and also from my first equation (I) is inversely proportional to ($r^2$). from these two we get $Sm^2$ is inversely proportional to $r^2$ i.e Sm is inversely proportional to r, which is against your conclusion that Sm is inversely proportional to $r^2$. Please explain

'V' is velocity of the wave in the medium, 'w2' is the angular velocity of wave and the that remaining one is the density of given medium.