急 ! Logarithmic Function EX3.

(a)let E1 and E2 be the amplitude of the seismic wave in the first and secong earthquake respectively.
logE1=1.5(8.1)+K.....(1)
logE2=1.5(7.5)+K......(2)
(1)-(2)
logE1-logE2=(1.5(8.1)+K)-(1.5(7.5)+K)
log(E1/E2)=1.5(8.1)-1.5(7.5)
=0.9
E1/E2=10^0.9
=8(corr.to the nearest integer)
the amplitude of the scismic wave in the first earthquake was 8 times as the second one.
(b)let E1 and E3 be the amplitude of the seismic wave in the first and third earthquake respectively,
logE1=1.5(8.1)+K......(1)
logE3=1.5(7.0)+K......(2)
(1)-(2)
logE1-logE3=(1.5(8.1)+K)-(1.5(7.0)+K)
log(E1/E3)=1.5(8.1)-1.5(7.0)
=1.65
E1/E3=10^1.65
=45(corr.to the nearest integer)
the amplitude of the scismic wave in the first earthquake was 45 times as the third one.
(b)let I W/m^2 be the sound intensity of a flying civil aircraft.
122=10log(10^12I)
12.2=log(10^12I)
10^12I=10^12.2
I=10^12.2/10^12
I=10^0.2
I=1.58(corr.to 3 sig.fig.)
intensity level of the moving car
=10log(10^12*10^0.2/10000)
=82dB.