Waves and Sound
From music to speech to the ripples on a pond, waves are everywhere, and sound is one of the most familiar. Waves carry energy without carrying matter, and a few simple properties describe them all. Understanding waves and sound is a core physics topic with a handy formula at its center.
This lesson covers wave properties and how sound behaves.
A wave is a disturbance that carries energy from one place to another without moving matter along with it. Waves are described by wavelength, frequency, and amplitude. Sound is a wave made of vibrations that travels through a material like air, and it needs a medium to travel.
What are the properties of a wave?
Every wave can be described by a few measurements. Wavelength is the distance between one peak and the next. Frequency is how many waves pass a point each second, measured in hertz. Amplitude is the height of the wave, which relates to how much energy it carries. These are connected to wave speed by a simple equation:
[ v = flambda ]where (v) is the wave speed, (f) is the frequency, and (lambda) is the wavelength. Higher frequency means shorter wavelength for the same speed.
| Property | Meaning |
|---|---|
| Wavelength | Distance between peaks |
| Frequency | Waves per second (hertz) |
| Amplitude | Height; relates to energy |
How does sound work?
Sound is a wave created by vibrations that push and pull on the particles of a material. Because it needs particles to travel, sound cannot move through the vacuum of space; it needs a medium like air, water, or solid. In sound, frequency is heard as pitch, so a high frequency sounds high, and amplitude is heard as loudness, so a bigger amplitude sounds louder. Sound also travels faster through solids and liquids than through air, because the particles are packed more closely.
Watch: A Short Video Lesson
GPB Education walks through this skill clearly in a few minutes. It is a helpful companion to the reading above:
A routine for wave questions
- Identify the property asked about: wavelength, frequency, or amplitude.
- Use (v=flambda) to connect speed, frequency, and wavelength.
- For sound, remember frequency is pitch and amplitude is loudness.
- Recall sound needs a medium and cannot travel through a vacuum.
- Know sound travels faster in denser materials.
Practice questions
- What is wavelength?
- Write the equation linking wave speed, frequency, and wavelength.
- What does a wave carry from place to place?
- In sound, what property do we hear as pitch?
- Why can’t sound travel through outer space?
- True or false: sound travels faster in air than in water.
Answers:
- The distance between one peak of a wave and the next.
- (v=flambda).
- Energy (without carrying matter along).
- Frequency.
- Because space is a vacuum with no particles to carry the vibrations.
- False. Sound travels faster in water because its particles are closer together.
Where this fits
Waves and sound connect to waves, heat, and temperature and to light in the electromagnetic spectrum. They carry the energy discussed in energy and simple machines. Find all topics on the ASVAB General Science Learning Hub.
Recommended Prep Books
These study guides and practice books help you keep building momentum as you prepare:
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