Chapter 12: Sound

Represent graphically by two separate diagrams in each case

(i) Two sound waves having the same amplitude but different frequencies?

(ii) Two sound waves having the same frequency but different amplitudes.

(iii) Two sound waves having different amplitudes and also different wavelengths.

Soln:

19. Establish the relationship between the speed of sound, its wavelength and frequency. If the velocity of sound in air is 340 m s–1, calculate

(i) wavelength when the frequency is 256 Hz.

(ii) frequency when the wavelength is 0.85 m

Soln:

Relationship between Sound speed, wavelength and frequency

Speed = distance/time

V = wavelength/time

V = wavelength × 1/time x wavelength x 1 /time

Frequency = 1/time

V = wavelength × frequency

1) Wavelength = speed/frequency

=340/256

= 1.32 m

2) Frequency = speed / wavelength

=340/0.85

= 400 HZ

20. Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound. Mark the position of compression and rarefaction on this curve. Also, define wavelengths and time periods using this curve.

Soln: