Grade 11: Waves & Sound 🌊🔊

Interactive Lesson • $\text{Transverse}$ $\text{vs.}$ $\text{Longitudinal}$ • $\vec{v}=f\lambda$ • $\text{Pitch}$ $\text{and}$ $\text{Loudness}$

What is a $\text{Wave}$? 🌀

  A **$\text{Wave}$** is a disturbance that $\text{transfers}$ $\text{energy}$ from one point to another without transferring $\text{matter}$. All waves require a **$\text{Medium}$** (the substance the wave travels through) except $\text{Electromagnetic}$ $\text{Waves}$ ($\text{light}$).

 
   

1. $\text{Transverse}$ $\text{Waves}$

   

The $\text{medium}$ $\text{moves}$ $\text{perpendicular}$ ($\mathbf{\perp}$) to the direction the $\text{energy}$ $\text{travels}$.

   

$\text{Examples}: \text{Water}$ $\text{waves}$, $\text{Light}$ ($\text{Electromagnetic}$ $\text{waves}$).

 
 
   

2. $\text{Longitudinal}$ $\text{Waves}$

   

The $\text{medium}$ $\text{moves}$ $\text{parallel}$ ($\mathbf{\parallel}$) to the direction the $\text{energy}$ $\text{travels}$.

   

$\text{Examples}: \text{Sound}$ $\text{waves}$, $\text{P}$-$\text{waves}$ ($\text{Seismic}$).

 
 
Score: 0
 
Streak: 0

Key $\text{Wave}$ $\text{Properties}$ and $\text{The}$ $\text{Wave}$ $\text{Equation}$ 📏

 
   

$\text{Amplitude}$ ($\text{A}$)

   

The maximum $\text{displacement}$ from the $\text{rest}$ $\text{position}$ ($\text{related}$ $\text{to}$ $\text{energy}$). $\text{Units}: \text{meters}$ ($\text{m}$).

 
 
   

$\text{Wavelength}$ ($\lambda$)

   

The distance between two consecutive identical points on a wave ($\text{e.g.,}$ $\text{crest}$ $\text{to}$ $\text{crest}$). $\text{Units}: \text{meters}$ ($\text{m}$).

 
 
   

$\text{Frequency}$ ($f$)

   

The number of $\text{waves}$ that $\text{pass}$ a $\text{fixed}$ $\text{point}$ per $\text{second}$. $\text{Units}: \text{Hertz}$ ($\text{Hz}$ or $\text{s}^{-1}$).

 
   

The $\text{Universal}$ $\text{Wave}$ $\text{Equation}$

   

The $\text{speed}$ ($\vec{v}$) of any wave is determined by its $\text{frequency}$ ($f$) and $\text{wavelength}$ ($\lambda$).

    $$\vec{v} = f \lambda$$

Sound $\text{Waves}$: $\text{Pitch}$ and $\text{Loudness}$ 🎶

  $\text{Sound}$ is a $\text{longitudinal}$ $\text{wave}$ created by $\text{vibrations}$ that travel through a $\text{medium}$.

 
   

$\text{Pitch}$

   

Our perception of a sound's $\text{frequency}$.

   

$\text{High}$ $\text{Frequency}$ $\longleftrightarrow$ $\text{High}$ $\text{Pitch}$

 
 
   

$\text{Loudness}$

   

Our perception of a sound's $\text{intensity}$ ($\text{energy}$), which is related to its $\text{Amplitude}$.

   

$\text{Large}$ $\text{Amplitude}$ $\longleftrightarrow$ $\text{Loud}$ $\text{Sound}$

 
 
   

$\text{Speed}$ $\text{of}$ $\text{Sound}$

   

The speed of sound depends only on the $\text{medium}$ ($\text{material}$ $\text{and}$ $\text{temperature}$). It travels $\text{fastest}$ in $\text{solids}$ and $\text{slowest}$ in $\text{gases}$.

 

Interactive $\text{Wave}$ $\text{Calculation}$ ($\vec{v} = f\lambda$) 🧮

Use the $\text{Universal}$ $\text{Wave}$ $\text{Equation}$ to calculate $\text{Wavelength}$.

   

Problem:

   

A $\text{sound}$ $\text{wave}$ travels at $340 \text{ m}/\text{s}$ and has a $\text{frequency}$ of $680 \text{ Hz}$. What is its $\text{wavelength}$ ($\lambda$)?

   

$$\text{Calculation}: \lambda = \frac{\vec{v}}{f} = \frac{340 \text{ m}/\text{s}}{680 \text{ Hz}} = ? \text{ m}$$

   
                $\text{m}$            
   

⚡ $\text{Wave}$ $\text{Concept}$ $\text{Check}$!

Identify the wave property or type best described by the scenario.

 
The $\text{maximum}$ $\text{displacement}$ of a rope from its $\text{rest}$ $\text{position}$.
 
     
 
 

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