COLLEGE PHYSICS
COLLEGE PHYSICS
2nd Edition
ISBN: 9781464196393
Author: Freedman
Publisher: MAC HIGHER
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Question
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Chapter 13, Problem 83QAP
To determine

(a)

The factor by which a point source moves away from the screen in order to lower the intensity by factor of 10.

Expert Solution
Check Mark

Answer to Problem 83QAP

The factor by which a point source moves away from the screen in order to lower the intensity by factor of 10 is 3.16.

Explanation of Solution

Given:

The intensity of the new wave is,
  I2=I110

Formula used:

The intensity of the sound wave is given by,
  I=P4πr2

Where,
  I =Intensity
  P =Power
  r =Distance

Calculation:

From inverse square law of sound waves, we get
  I=P4πr2I11r12I21r22

   I 1 10I1=r12r22110=r12r22

  r22=10r12

  r2=r110r2=3.16r1

Conclusion:

By factor 3.16 the point source of sound wave moves away from the screen.

To determine

(b)

The factor by which a point source moves away from the screen in order to lower the intensity by factor of 3.

Expert Solution
Check Mark

Answer to Problem 83QAP

The factor by which a point source moves away from the screen in order to lower the intensity by factor of 3 is 1.73.

Explanation of Solution

Given:

The intensity of the new wave is,
  I2=I13

Formula used:

The intensity of the sound wave is given by,
  I=P4πr2

Where,
  I =Intensity
  P =Power
  r =Distance

Calculation:

From inverse square law of sound waves, we get
  I=P4πr2I11r12I21r22

   I 1 3I1=r12r2213=r12r22

  r22=3r12

  r2=r13r2=1.73r1

Conclusion:

By factor 1.73 the point source of sound wave moves away from the screen.

To determine

(c)

The factor by which a point source moves away from the screen in order to lower the intensity by factor of 2.

Expert Solution
Check Mark

Answer to Problem 83QAP

The factor by which a point source moves away from the screen in order to lower the intensity by factor of 2 is 1.41.

Explanation of Solution

Given:

The intensity of the new wave is,
  I2=I12

Formula used:

The intensity of the sound wave is given by,
  I=P4πr2

Where,
  I =Intensity
  P =Power
  r =Distance

Calculation:

From inverse square law of sound waves, we get
  I=P4πr2I11r12I21r22

   I 1 2I1=r12r2212=r12r22

  r22=2r12

  r2=r12r2=1.41r1

Conclusion:

By factor 1.41 the point source of sound wave moves away from the screen.

To determine

(d)

The changes observed when the point source is replaced with hemispherical instead of spherical.

Expert Solution
Check Mark

Explanation of Solution

Introduction:

The intensity of sound wave at a distance due to a spherical point source is given by inverse square law of sound.

  I=P4πr2

From inverse square law of sound waves, we get
  I=P4πr2

For hemisphere the surface area is given by,
Surfacearea=3πr2

Thus, intensity is given by
  I=P3πr2

When the shape of point source is changed from spherical to hemispherical the intensity of it is increased and becomes P3πr2.

Conclusion:

By changing the point source from spherical to hemispherical the intensity is I=P3πr2

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Chapter 13 Solutions

COLLEGE PHYSICS

Ch. 13 - Prob. 11QAPCh. 13 - Prob. 12QAPCh. 13 - Prob. 13QAPCh. 13 - Prob. 14QAPCh. 13 - Prob. 15QAPCh. 13 - Prob. 16QAPCh. 13 - Prob. 17QAPCh. 13 - Prob. 18QAPCh. 13 - Prob. 19QAPCh. 13 - Prob. 20QAPCh. 13 - Prob. 21QAPCh. 13 - Prob. 22QAPCh. 13 - Prob. 23QAPCh. 13 - Prob. 24QAPCh. 13 - Prob. 25QAPCh. 13 - Prob. 26QAPCh. 13 - Prob. 27QAPCh. 13 - Prob. 28QAPCh. 13 - Prob. 29QAPCh. 13 - Prob. 30QAPCh. 13 - Prob. 31QAPCh. 13 - Prob. 32QAPCh. 13 - Prob. 33QAPCh. 13 - Prob. 34QAPCh. 13 - Prob. 35QAPCh. 13 - Prob. 36QAPCh. 13 - Prob. 37QAPCh. 13 - Prob. 38QAPCh. 13 - Prob. 39QAPCh. 13 - Prob. 40QAPCh. 13 - Prob. 41QAPCh. 13 - Prob. 42QAPCh. 13 - Prob. 43QAPCh. 13 - Prob. 44QAPCh. 13 - Prob. 45QAPCh. 13 - Prob. 46QAPCh. 13 - Prob. 47QAPCh. 13 - Prob. 48QAPCh. 13 - Prob. 49QAPCh. 13 - Prob. 50QAPCh. 13 - Prob. 51QAPCh. 13 - Prob. 52QAPCh. 13 - Prob. 53QAPCh. 13 - Prob. 54QAPCh. 13 - Prob. 55QAPCh. 13 - Prob. 56QAPCh. 13 - Prob. 57QAPCh. 13 - Prob. 58QAPCh. 13 - Prob. 59QAPCh. 13 - Prob. 60QAPCh. 13 - Prob. 61QAPCh. 13 - Prob. 62QAPCh. 13 - Prob. 63QAPCh. 13 - Prob. 64QAPCh. 13 - Prob. 65QAPCh. 13 - Prob. 66QAPCh. 13 - Prob. 67QAPCh. 13 - Prob. 68QAPCh. 13 - Prob. 69QAPCh. 13 - Prob. 70QAPCh. 13 - Prob. 71QAPCh. 13 - Prob. 72QAPCh. 13 - Prob. 73QAPCh. 13 - Prob. 74QAPCh. 13 - Prob. 75QAPCh. 13 - Prob. 76QAPCh. 13 - Prob. 77QAPCh. 13 - Prob. 78QAPCh. 13 - Prob. 79QAPCh. 13 - Prob. 80QAPCh. 13 - Prob. 81QAPCh. 13 - Prob. 82QAPCh. 13 - Prob. 83QAPCh. 13 - Prob. 84QAPCh. 13 - Prob. 85QAPCh. 13 - Prob. 86QAPCh. 13 - Prob. 87QAPCh. 13 - Prob. 88QAPCh. 13 - Prob. 89QAPCh. 13 - Prob. 90QAPCh. 13 - Prob. 91QAPCh. 13 - Prob. 92QAPCh. 13 - Prob. 93QAPCh. 13 - Prob. 94QAPCh. 13 - Prob. 95QAPCh. 13 - Prob. 96QAPCh. 13 - Prob. 97QAPCh. 13 - Prob. 98QAPCh. 13 - Prob. 99QAPCh. 13 - Prob. 100QAPCh. 13 - Prob. 101QAPCh. 13 - Prob. 102QAPCh. 13 - Prob. 103QAPCh. 13 - Prob. 104QAPCh. 13 - Prob. 105QAPCh. 13 - Prob. 106QAPCh. 13 - Prob. 107QAPCh. 13 - Prob. 108QAPCh. 13 - Prob. 109QAPCh. 13 - Prob. 110QAPCh. 13 - Prob. 111QAPCh. 13 - Prob. 112QAPCh. 13 - Prob. 113QAP
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