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

9:4

2:3

3:2

4:9

Solution

9:4

The average power per unit area that is incident perpendicular to the direction of propagation is called the intensity.

Intensity of sound

$I = \frac{P}{4 {πr}^{2}} \Rightarrow i \propto \frac{1}{r^{2}} (intensity \propto \frac{1}{{distance}^{2}}) \Rightarrow \frac{I_{1}}{I_{2}} = {(\frac{r_{1}}{r_{2}})}^{2} Here r_{1} = 2 m, r_{2} = 3 m$

Substiting the values, we have

$\frac{I_{1}}{I_{2}} = {(\frac{3}{2})}^{2} = \frac{9}{4}$

Some More Questions From Waves Chapter

When two tuning forks (fork 1 and fork 2) are sounded simultaneously, 4 beats per second are heard. Now, some tape is attached on the prong of the fork 2. When the tuning forks are sounded again, 6 beats per seconds are heard. If the frequency of fork 1 is 200 Hz, then what was the original frequency of fork 2?

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Waves

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

9:4

2:3

3:2

4:9

Some More Questions From Waves Chapter

The sound waves after being converted into electrical waves are not transmitted as such because

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For Daily Free Study Material Join wiredfaculty

Waves

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distance of 2m and 3m respectively from the source. The ratio of the intensities of the waves at P and Q is 9:4 2:3 3:2 4:9

Some More Questions From Waves Chapter

The sound waves after being converted into electrical waves are not transmitted as such because

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

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

9:4

2:3

3:2

4:9