Speed of Sound in Air

Course: Section: Name(s): Instructor: Date:

Introduction and Objectives : Waves propagate the energy from particles in motion. They are classified as transverse or longitudinal. In transverse waves, the particle displacement is perpendicular to the motion of the wave. In longitudinal waves, the particle displacement is in the same direction as the motion of the wave. All waves have the fundamental properties of velocity, wavelength, period, frequency and amplitude. Velocity: distance traveled per unit time (meters/second). Wavelength: distance between two similar points on any two consecutive waves (meters) Period: time required for one wavelength to travel through a specified point (seconds) Frequency: number of vibrations per unit time (Hertz).

Period = 1/frequency or T = 1/f velocity = wavelength x frequency or v = λf

Equipment Required : Tuning forks, pipe, beaker with water, ruler Lab Procedures:

Figure 1:

With the help of a resonance apparatus as shown in fig 1, we can determine the wavelength and velocity of sound waves.

Take a tuning fork (preferably with a frequency of 480 or 512 or 523.2 Hz). Set the tuning fork into vibration by striking it with a rubber hammer. Immerse the pipe in a cylinder of water, hold the tuning fork above the pipe and adjust the height of the water level in the pipe till you hear the loudest sound. This is the resonant frequency and corresponds to λ/4. You will hear loudest sound when the height h is a quarter of a wavelength, or an odd-numbered multiple of a quarter-wavelength (λ/4, 3λ/4, 5λ/4).

Record your observations and calculations in the table below:

Data Tables : The velocity of sound in air is given by v = 332 + (0.60)T

where: v = velocity of sound in air 332 m/s = velocity of sound in air at 0˚ Celsius T = temperature of air in degrees Celsius

Table 1: Room temperature Velocity at Room Temp = 332 + (0.60)T T (˚C)

Table 2: Frequency (f) height (h) = λ/4 λ (meters) v = λf (meters/sec) Percent error (%) Hz (meters)

Percent error = [(|Experimental – Accepted|)/Accepted] x 100% (Note: “Accepted” is the velocity you obtained at Room Temp in Table 1) Answers to questions :

1. Define wave motion, and give an example of a wave.

2. Distinguish between longitudinal and transverse waves.

3. Define the velocity, wavelength, and frequency of a wave and give the symbols for each.

4. State the relationship between velocity, wavelength, and frequency of a wave.

5. Define amplitude of a wave.

Conclusions: