Answer:
Explanation:
If I is the intensity of first sound echo, then with each subsequent echo the sound gets softer by 5 %.
At t=0.8, s I=I0
At t=2*0.8 s=1.6 s, I=Io-I0*5/100
At t=3*0.8 s=2.4 s, I= (Io-I0*5/100)-(5/100)* (Io-I0*5/100)= (Io-I0*5/100)[1-0.05]
At t=4*0.8 s=3.2 s,I=(Io-I0*5/100)-(5/100)* (Io-I0*5/100)-(5/100) Io-I0*5/100)-(5/100)* (Io-I0*5/100)= (Io-I0*5/100)[1-0.05][1-0.05]= (Io-I0*5/100)[1-0.05]2
So,
I(n)=I0 for n=1
I(n)= (Io-I0*5/100)[1-0.05]n-2 for n=2 or n>2