A point source is emitting sound waves of intensity 16 × 10 - 8 W m - 2 at the origin. The difference in intensity (magnitude only) at two points located at a distances of 2 m and 4 m from the origin respectively will be ________ × 10 - 8 W m - 2 .

Step-by-step solution

Intensity for a point source varies as I ∝ 1 r 2 . Intensity at a distance of 2 m , I 2 = 16 × 10 - 8 × 1 2 2 = 4 × 10 - 8 W m - 2 Similarly, intensity at a distance of 4 m , I 4 = 16 × 10 - 8 × 1 4 2 = 1 × 10 - 8 W m - 2 Required difference, I 2 - I 4 = 3 × 10 - 8 W m - 2