Question

intensity of sound waves from point source at distance r from the source is I .the intensity at distance 2r will be?​

Answer 1

Answer:

Given:

Intensity of sound from a distance of "r" is "I"

To find:

Intensity at a distance of "2r"

Concept:

Intensity refer to Energy generated per unit area, per unit time. So it's SI unit is watt/m².

If we keep "time" and "energy generated" constant, then Intensity of sound is inversely proportional to square of distance.

I ∝ 1/r²

Formulas used:

Let energy be "E", time be "T", distance be "r".

I = E/(Tr²)

Calculation:

I1 = E/(Tr²)

Again,

I2 = E/{T(2r)²}

=> I2 = E/(T × 4r²)

=> I2 = (1/4) × E/(Tr²)

So, I2/I1 = 1/4

=>I2 = (1/4) × I1 = I/4

So the answer is I/4

Answer 2

Thanks for asking your question!

$\huge\bf{Answer:-}$

According to the given question:

• Intensity of sound waves from point source at distance r from the source is I .

• The intensity at distance 2r will be ( find ) .

• According to this question energy produced per unit of a area with unit of time is equal to ( SI unit ).

• SI unit is equal to (Watt / m²) This is watt by meter square.

• The sound is inversely proportional to the distance .

Using formula :-

I = E / Tr²

= I1 E / ( Tr² )

= I2 = E / T ( 2r)²

= I2 = ( I / 4 ) × E / Tr²

= I2 / I1 = 1 / 4

= I2 = ( 1 / 4 ) × I4 = 1 / 4