Practice portal › Waves › Superposition, Interference and Intensity

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances of 2 m and 3 m respectively from the source. The ratio of the intensities of the waves at P and Q is

Asked in NEET 2005 · Sound intensity and decibels

• (1) 3:2
• (2) 2:3
• (3) 9:4
• (4) 4:9

Step-by-step solution

Why the other options are wrong

• (1) Is the ratio of the distances, not of the intensities; intensity falls as the square of the distance.
• (2) Is that ratio inverted as well.
• (4) Squares the distances but puts them the wrong way up; the nearer point P has the greater intensity.

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.