Wavelength and Sound

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Experiment 7: Velocity of Sound
Laboratory Report
Hazel Guerrero, Kyle Iddoba, Matthew Jocson, Thea Lagman
Department of Biological Sciences
College of Science, University of Santo Tomas
Espanya, Manila Philippines

Verification of the relationship between frequency of sound and its wavelength and the determination of the velocity and the speed of sound in different mediums was the main focus of this experiment. The speed of sound and its velocity was determined using the resonance tube apparatus and Kundt’s tube respectively. A vernier microphone was used to note the time interval between wavelengths. The results obtained on the second and third experiment gathered a minimal compared error compared to the first experiment. Introduction

Sound is a longitudinal wave in a medium. Sound waves usually travel out in all directions from the source of sound, with an amplitude that depends on the direction and distance from the source.

A sound wave is a pressure disturbance that travels through a medium by means of particle-to-particle interaction. As one particle becomes disturbed, it exerts a force on the next adjacent particle, thus disturbing that particle from rest and transporting the energy through the medium. Like any wave, the speed of a sound wave refers to how fast the disturbance is passed from particle to particle. While frequency refers to the number of vibrations that an individual particle makes per unit of time, speed refers to the distance that the disturbance travels per unit of time.

The speed of any wave depends upon the properties of the medium through which the wave is traveling. The phase of matter has a tremendous impact upon the elastic properties of the medium. In general, solids have the strongest interactions between particles, followed by liquids and then gases. For this reason, longitudinal sound waves travel faster in solids than they do in liquids than they do in gases.

The objectives of this experiment is to verify the relationship between frequency of sound and its wavelength, to determine the speed of sound by means of a resonating air column and lastly, to determine the velocity if sound in a solid using a vibrating rod.

The formula used in to get the velocity of sound is;
V = fλ
V = Velocity
f = Frequency engraved in the tuning fork
λ = Computed wavelength of sound produced
The formula used to get the wavelength λ is:
λ = 4L + 0.3D
λ = Wavelength
L = Change in level of the water
The formula used to get the theoretical velocity of air is: V = 331 + 0.6T

V = velocity
T = Temperature of the water in degrees Celsius
The formula used to get the Frequency of sound produced is: f = V/λ
f = Frequency produced
V = Theoretical velocity obtained in Activity 1
λ = Twice the average if the distances between two consecutive displacement nodes
The formula used to get the speed of sound (Vr) is:
Vr = fλr
Vr = Speed of sound
f = Frequency of the sound and
λr = Wavelength of sound in the rod
The formula used to get the wavelength of sound in the rod is: λr = 2L
λr = Wavelength of sound in the rod
L = Distance between two nodes

The Formula used to get the theoretical speed of Sound in the rod is: Vr

Vr = Theoretical velocity of sound in solid
Y = Young’s modulus (2.0x1011 n/m2)
ρ = Density of steel (7860 kg/m3)
Activity 1
The resonance tube apparatus was filled with completely. A tuning fork was struck with a rubber mallet. The vibrating tuning fork was placed over the top of the glass tube. The water vessel was slowly lowered until the loudest sound was heard. The point where the sound was heard was marked. The vibration of the fork was made sure as the vessel was lowered. The fork was struck again if the vibration stopped. The distance between the point where the loudest sound was heard and the top of the glass tube was measured. This was recorded as L. The data gathered was converted to meters. The diameter of...
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