The intensity of the sound wave reaching your ear from a car radio 140 m away from you is 0.050 W/m2. The car drives toward you, so that the distance between you and the radio has decreased to one-fourth of its original value. Determine the new intensity of the sound reaching your ear.

Answer: intensity (I2) = 0.8W/m²

Explanation: The relationship between the intensity of sound wave obeys the inverse square law, that's the intensity (I) is inversely proportional to square of distance (r).

I α r², I = kr²

I1 * (r1) ² = I2 * (r2) ²

From the question,

I1 = 0.050W/m², r1 = 140m, I2 = ?, r2 = 1/4 * 140 = 35m.

By substituting the parameters, we have that

0.05 * (140) ² = I2 * (35) ²

0.05 * 19600 = I2 * 1225

980 = I2 * 1225

I2 = 980/1225

I2 = 0.8W/m²