Answer
$8.044$
Work Step by Step
Using relation $M=\log \dfrac{I}{S}$ ...(1)
As we are given that $S=10^{-4}, M=6.5$
Equation (1) becomes: $M=\log \dfrac{I}{S} \implies I= S10^{M}$
$\implies I=(10^{-4}) (10^{6.5})=10^{(2.5)}$
Now, for $I= 35 \times 10^{(2.5)}$
we have $M=\log [\dfrac{35 \times 10^{(2.5)}}{10^{-4}}]=8.044$
