What is a Wave?

Chapter 12 Section 3Glencoe Pages 452-458

I. Types of waves

A. What is a wave?

1. Wave – a disturbance that carries energy

through matter or space

the matter moves very little

the energy moves

Most waves travel through a medium

2. Most waves travel through a medium

a. medium – matter through which a

wave travels

ripples in a pond move through water

sound waves travel through the air

Mechanical waves

b. Mechanical waves – waves that require a

medium to travel

almost all waves are of this type

Electromagnetic waves

c. Electromagnetic waves – waves caused by electric and magnetic fields that do not require a medium

Electromagnetic spectrum of waves,

consisting of: Radio waves, Microwaves, Infrared waves, Visible

light, Ultraviolet waves, X-rays, and Gamma rays

Electromagnetic waves

Electromagnetic waves

Electromagnetic waves

Wave Energy3. Waves transfer energy energy is the ability to do work waves have energy therefore waves can do work

example: water waves on a boat

Wave Energy

Example: light waves on the eyes

Wave Energy

Example: sound waves on your eardrum

*Bigger waves carry more energy

Wave Energy

4. Energy may spread out as a wave travels

- sound waves, ripples in a pond move out

in circular patterns called wave fronts,

and get bigger farther from the source

and the energy spreads out along the

entire wave front

B. Vibrations and waves1. Most waves are created

by a vibrating

object

2. Vibrations involve a

transformation of

energy, generally

between potential

and kinetic

C. Transverse and longitudinal waves

1. Particles in a medium can vibrate up

and down or back and forth

2. Waves are classified by the direction of

particle movement

Transverse and longitudinal waves

3. Transverse waves – waves causing the particles of the medium to vibrate perpendicular to the direction the wave is traveling.Ex. Crowd doing the wave, light waves

Link to waves

Transverse and longitudinal waves

4. Longitudinal waves – waves causing the medium particles to move parallel to the wave’s direction of travel

squeezing together (compression) spreading apart (rarefactions)

ex. Sound waves

Surface waves

5. Surface waves – occur at boundaries between different mediums

air and water

- these waves move both in a transverse and a longitudinal way.

Wave Properties and Forms

Chapter 12 Section 3: Holt Physics

Continued

II. Two Basic Wave Forms

A. Pulse wave – a single non-periodic wave

A single traveling wave

Example:

II. Two Basic Wave Forms

B. Periodic wave – wave whose source is

some form of periodic motion

Bouncing spring, wave machine

Example:

III. Wave properties A. Transverse waves look like a sine curve (looks

like an “S” on its side)

- example drawing – all parts labeled

I. Wave properties

Transverse wave picture

- sine waves with the shape of a sine curve- Waves whose particles move

perpendicular to the direction of wave

motion

B. Parts of a transverse wave1. Crest – highest point on a transverse wave

2. Trough – lowest point on a transverse wave

3. Amplitude – greatest distance a particle is displaced from its normal resting position

B. Parts of a transverse wave4. Wavelength – distance between 2

successive identical points on a wave

symbol = (lambda) measured in meters

C. Longitudinal waves1. No crests or troughs2. Compressions and rarefactions (stretched)- example drawing of longitudinal wave (click on

picture)

C. Longitudinal waves Wave whose particles move parallel to the direction

of wave motion

Compressions – areas where the medium is squeezed together closer than at equilibrium

Rarefactions – areas where the medium is stretched or expanded farther apart than at equilibrium

One wavelength is from compression to compression or rarefaction to rarefaction

Longitudinal Waves

Longitudinal waves examples

Example #1

Example #2

IV. Period, Frequency, and Wavespeed The source of the vibration determines the frequency

Frequency (f)– number of wavelengths that pass a point in 1 second measured in hertz (Hz) named after Heinrich Hertz (1888) 1 Hz = 1 wavelength (vibration) per second

can hear 20 Hz (low) 20,000 Hz (high)

Frequency of a vibrating object = frequency of a wave Frequency (f) = # of vibrations per second # vibrations / time

IV. Period, Frequency, and Wavespeed Wavespeed = frequency x wavelength

V (m/s) = f (hz) x (m)

The wavespeed of a mechanical wave is constant for a given medium

Period (T) – time required for one full wavelength to pass a certain point (measured in seconds)