Waves

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 distances of 2 m and 4 m from the origin respectively will be 10-8 W m-2.

Answer

BONUS

Solution

Point source: I= P4 r2 1r2

At the source itself (r 0) I , so an "intensity at the origin" does not fix the power P ⇒ data incomplete

Intended reading (16 10-8 W m-2 at r=1 m): I2= 1622=4, I4= 1642=1 (in 10-8 W m-2)

|I2-I4|=3 10-8 W m-2

Answer: Bonus (full marks to all who attempted)

Note: The official NTA answer key gives 3. Our faculty team finds that the question cannot be answered from the given data, so this question should be dropped (bonus: full marks to everyone who attempted it).