Final answer:
The intensity of the sound, when I = 10^-9 W/m^2, is 30 dB.
Step-by-step explanation:
The equation to calculate the intensity of a sound in decibels (dB) is given by I(dB) = 10 * log10(I / I0), where I is the intensity of the sound and I0 is the threshold of hearing intensity.
To find the intensity, in decibels, when I = 10-9 W/m2, we substitute I = 10-9 and I0 = 10-12 into the equation:
I(dB) = 10 * log10((10-9) / (10-12))
I(dB) = 10 * log10(103)
I(dB) = 10 * 3
I(dB) = 30 dB
Therefore, the intensity of the sound, when I = 10-9 W/m2, is 30 dB.