(WVS) Wave Speed Lesson

Wave Speed

The speed of a longitudinal wave is defined as the same as the speed of transverse waves. Wave speed is the distance a wave travels per unit time. Wave speed can be calculated by using the following equation:

v = λ · f

  • v = wave speed measured in m/s.
  • λ = wavelength measured in meters.
  • f = frequency of wave measured in Hertz.

Example Problem:

  • The musical note "A" is a sound wave. The note has a frequency of 440 Hz and a wavelength of 0.784 m. Calculate the speed of the musical note.

Given:

Frequency = 440 Hz

Wavelength = 0.784 m

Solution:

v = λ · f

v = 0.784 m · 440 Hz

v =   345 m/s

Example Problem:

  • A flute produces a musical sound traveling at a speed of 320 m/s. The frequency of the note is 256 Hz. Calculate the wavelength.

Given:

Frequency = 256 Hz

Speed = 320 m/s

Solution:

v = λ · f

Rearrange the equation to find wavelength:

λ = v/f

λ = 320m/s/256Hz

λ = 1.25 meters

Speed of Sound

The speed of sound depends on the medium the sound is traveling in. Sound travels faster in solids than in liquids, and faster in liquids than in gases. This is because the density of solids is higher than that of liquids, which means that the particles are closer together. Sound can be transmitted more easily. Remember that sound is a vibration of kinetic energy passed from molecule to molecule. The closer the molecules are to each other and the tighter their bonds, the less time it takes for them to pass the sound to each other and the faster sound can travel. It is easier for sound waves to go through solids than through liquids because the molecules are closer together and more tightly bonded in solids. Similarly, it is harder for sound to pass through gases than through liquids, because gaseous molecules are farther apart. So in summary, the speed of sound is faster in solid materials and slower in liquids or gases.

The speed of sound also depends on the temperature of the medium. The hotter the medium is, the faster its particles move and therefore the quicker the sound will travel through the medium. When we heat a substance, the particles in that substance have more kinetic energy and vibrate or move faster. Sound can therefore be transmitted more easily and quickly in hotter substances.

Sound waves are pressure waves. The speed of sound will therefore be influenced by the pressure of the medium through which it is traveling. At sea level, the air pressure is higher than high up on a mountain. Sound will travel faster at sea level where the air pressure is higher than it would at places high above sea level.

[CC BY 4.0] UNLESS OTHERWISE NOTED | IMAGES: LICENSED AND USED ACCORDING TO TERMS OF SUBSCRIPTION