Wave Basics & Properties of Sound question from JEE Main 2019 (12 Apr, Shift 2)

Answer: (c)

1. Sound level $L = 10\log_{10}(I/I_0)$, so $120 = 10\log_{10}(I/10^{-12})$ gives $I = 1\ \text{W/m}^2$.
2. Point source: $I = \dfrac{P}{4\pi r^2} \Rightarrow r = \sqrt{\dfrac{P}{4\pi I}} = \sqrt{\dfrac{2}{4\pi \times 1}}$
3. $r = \sqrt{0.159} \approx 0.40\ \text{m}$
4. So the answer is (c) $40\ \text{cm}$.