Physics · StudentHub Lesson
Waves & Sound
How waves transfer energy and how sound is produced and travels.
What you will learn
- Define wave properties like wavelength and frequency
- Distinguish transverse and longitudinal waves
- Explain how sound waves are produced
- Describe how sound travels through different media
- Relate pitch and volume to wave properties
Watch the lesson
Sound: Crash Course Physics #18 · CrashCourse
Watch on YouTubeTopic notes
Main Idea
Waves transfer energy without transferring matter, and sound is a longitudinal wave caused by vibrations traveling through a medium.
Key Concepts
- Waves have wavelength, frequency, and amplitude
- Sound waves are longitudinal, with compressions and rarefactions
- Sound needs a medium (solid, liquid, or gas) to travel
Definitions
- Wavelength: distance between successive wave crests
- Frequency: number of wave cycles per second, measured in Hertz
- Amplitude: the height of a wave, related to energy/loudness
Processes
Vibrating objects create pressure waves in a medium; these compressions and rarefactions travel outward as sound.
Equation
v = f * lambda (wave speed = frequency x wavelength)
Examples
A guitar string vibrating produces sound waves that travel through air to reach our ears.
Common Mistakes
- Thinking sound can travel through a vacuum
- Confusing amplitude with frequency
- Mixing up transverse and longitudinal waves
Key concepts
Important terms
- Frequency
- The number of wave cycles that pass a point per second, measured in Hertz.
- Amplitude
- The maximum displacement of a wave, related to its energy.
- Longitudinal wave
- A wave where particle vibration is parallel to the direction of wave travel, like sound.
Worked examples
Problem
A sound wave has a frequency of 440 Hz and wavelength of 0.78 m. Find its speed.
- 1. Use v = f * lambda
- 2. v = 440 * 0.78
Answer: approximately 343 m/s
Quick revision
- Waves transfer energy not matter
- Sound is a longitudinal wave
- Frequency relates to pitch
- Amplitude relates to loudness
- Sound needs a medium
- v = f x wavelength
- Sound cannot travel through a vacuum
Check your understanding
Question 1 · Multiple choice
What type of wave is sound?
Question 2 · Multiple choice
What determines the pitch of a sound?
Question 3 · True or false
Sound can travel through a vacuum.
Question 4 · Short answer
What quantity determines the loudness of a sound?
Question 5 · Short answer
If frequency is 500 Hz and wavelength is 0.68 m, find wave speed.
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