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# Waves

## Contents

Simple harmonic motion

Interference and superposition

Waves in 2 dimensions, and refraction

What is sound? How do we hear it?

Actually see the speed of sound at a Queen concert

Sources of sound: String instruments, harmonics, wind instruments, quality of sound

Doppler Effect

Diffraction: The way that waves spread around an obstacle

Discovering Fresnel diffraction: The Greatest Mistake In The History Of Physics

MCAS Physics exam: sample wave problems

## External resources

SalfordAcoustic offers high speed video and animations to help explain waves and acoustics. Salfordacoustics

## Fun topics

How do record players and vinyl LPs work?

Anomalous sounds (sound “mirages”?!)

Sonar, echolocation, and ultrasound

Facts and Fiction of the Schumann Resonance

Giant waves from the undersea canyon, Portuguese town of Nazaré

isvr.soton.ac.uk

## Metric units of the wave equation

### 1/s = 1 Hz

Heinrich Rudolf Hertz

Watt is love? Baby Don’t Hertz Me, No Morse 😉

Oh… My head Hertz from the Frequency of These puns…

## 2 types of waves: mechanical and light

### Here we see waves of dirt and rock, in an Earthquake.

Tarbuck & Lutgens

## Electromagnetic waves

### In the real world one can’t actually see an EM wave from the side. We can only see light if it hits our eyes.

as the wave moves through space,
the E (electric) field increases and decreases,
the B (magnetic) field increases and decreases.

## Waves can be  reflected, absorbed, or transmitted

### And some of the wave is transmitted (goes through to the other side)

More details on Dan Russell’s tutorial on how waves reflect, when they hit a boundary.

## Wave interference

What happens when 2 waves collide with each other? We get superposition, interference, standing waves,  nodes and antinodes. See these resources.

Interference-and-superposition (Kaiserscience)

Dan Russell’s excellent tutorial on wave superposition

more examples of waves interacting with each other.

## Longitudinal and Transverse waves

### From Dan Russell

While teaching undergraduate physics at Kettering University for 16 years, I was often frustrated with the depiction of standing sound waves in pipes as it was presented in most elementary physics textbooks… The solution: an animation to visualize particle motion and pressure for longitudinal sound waves….I created the animation below and its accompanying description in an attempt to better explain the behavior of a standing sound wave in a pipe.  Standing Sound Waves (Longitudinal Standing Waves)

### Transverse waves

The Mexican Wave. First seen internationally at the 1986 World Cup in Mexico City. It appeared at American football games for a few years before that.

## Earthquake waves

Seismic Waves is a browser-based tool to visualize the propagation of seismic waves from historic earthquakes through Earth’s interior and around its surface. Easy-to-use controls speed-up, slow-down, or reverse the wave propagation. By carefully examining these seismic wave fronts and their propagation, the Seismic Waves tool illustrates how earthquakes can provide evidence that allows us to infer Earth’s interior structure. See Seismic Waves Viewer

### S-waves (Shear) – Transverse waves that travel through the Earth

Earth Science, Tarbuck & Lutgens, Chapter 8

### P-waves (pressure) – longitudinal waves, aka compression waves.

Earth Science, Tarbuck & Lutgens, Chapter 8

Only longitudinal waves can propagate through a fluid, because any transverse motion would not experience any restoring force since a fluid is readily deformable. This fact was used by geophysicists to infer that a portion of the Earth’s core must be liquid: after an earthquake, longitudinal waves are detected diametrically across the Earth, but not transverse waves

Then the 2 types of waves can combine

Tarbuck & Lutgens

### External resources

Dan Russell’s excellent tutorial on waves

Physics of sound waves – University of Salford

PhET Radio waves and electric fields app

PhET Sound waves app

Uses of Waves: GCSE Physics review, at S-Cool

## Self-guided tutorials

Self guided tutorial on colors, spectrum and EM waves

Basic EM wave properties Physlet

Visulaize propagation of an EM wave I

Visualize propagation of an EM wave II

## Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS4-1. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling within various media. Recognize that electromagnetic waves can travel through empty space (without a medium) as compared to mechanical waves that require a medium

SAT subject test in Physics: Waves and optics

• General wave properties, such as wave speed, frequency, wavelength, superposition, standing wave diffraction, and Doppler effect
• Reflection and refraction, such as Snell’s law and changes in wavelength and speed
• Ray optics, such as image formation using pinholes, mirrors, and lenses
• Physical optics, such as single-slit diffraction, double-slit interference, polarization, and color