Waves

Textbook pages 92-99

Perception of Light & Sound

What is a WAVE?

A disturbance that travels through a medium

What is a WAVE?

A disturbance that travels through a medium Medium: a substance that carries the

disturbance from one location to another

What is a WAVE?

A disturbance that travels through a medium Medium: a substance that carries the

disturbance from one location to another▪ How? The particles of the medium interact

with particles next to them allowing the disturbance to travelExamples of a medium

Water Air Ground

What is a WAVE?

Transports energy from one place to another

What is a WAVE?

Transports energy from one place to another

What is a WAVE?

Transports energy from one place to another Particles of the medium are only

temporarily displaced from the rest position

What is a WAVE?

Transports energy from one place to another Particles of the medium are only

temporarily displaced from the rest position▪ Does not transport matter

Wave Characteristics

PropagationAmplitudeWavelengthFrequency

Propagation

Waves are distinguished by the way they propagate through a medium

Propagation

Transverse Waves Propagates perpendicular to the motion

of the mediumMOTION OF

THE MEDIUM

WAVE MOTION

Propagation

Transverse WavesCREST

TROUGH

Equilibrium

Propagation

Longitudinal Waves Propagates parallel to the motion of the

mediumWAVE MOTION

MOTION OF THE MEDIUM

Propagation

Longitudinal Waves Propagates parallel to the motion of the

mediumWAVE MOTION

MOTION OF THE MEDIUM

Propagation

Longitudinal Waves Propagates parallel to the motion of the

mediumWAVE MOTION

MOTION OF THE MEDIUM

Propagation

Longitudinal Waves Propagates parallel to the motion of the

mediumRegion of Compression

Region of Rarefaction

Amplitude (A)

Related to the amount of energy transferred by a wave

Amplitude (A)

Transverse Waves Maximum distance travelled by a

particle in the medium compared to its equilibrium position

Equilibrium

Amplitude (A)

Transverse Waves Depends on energy transmitted by the

waveENERGY AMPLITUDE

Amplitude (A)

Longitudinal Waves How tightly the medium is pushed together at

the compressions REGION OF LOW-DENSITY

COMPRESSION

REGION OF HIGH-DENSITY COMPRESSION

Amplitude (A)

Longitudinal Waves Depends on the density of compression

DENSITY AMPLITUDE

Wavelength ()

Length of a wave’s complete cycle Transverse Waves

Cycle

Wavelength () Length of a wave’s complete cycle

Longitudinal Waves

Cycle

Frequency (f)

Number of cycles per unit of time Measured in Hertz (Hz) – the number of

cycles per second 1 Hz = completes one full cycle in one second

Cycle Cycle

Speed at which a Wave TravelsSpeed of a wave depends on

Medium it travels in Temperature

Determine the speed at which a Wave TravelsSpeed = frequency x wavelength

Determine the speed at which a Wave TravelsSpeed = frequency x wavelength

v = f x v = speed (m/s) f = frequency (Hz) = wavelength (m)

Determine the speed at which a Wave Travels What is the speed of a sound wave

that has a wavelength of 2.00m and a frequency of 170.5Hz?

G

R

A

S

P

Determine the speed at which a Wave Travels What is the speed of a sound wave

that has a wavelength of 2.00m and a frequency of 170.5Hz?

G

R

A

S

P

f = 170.5Hz = 2.00m

Determine the speed at which a Wave Travels What is the speed of a sound wave

that has a wavelength of 2.00m and a frequency of 170.5Hz?

G

R

A

S

P

f = 170.5Hz = 2.00m

v = ?

Determine the speed at which a Wave Travels What is the speed of a sound wave

that has a wavelength of 2.00m and a frequency of 170.5Hz?

G

R

A

S

P

f = 170.5Hz = 2.00m

v = ?

v = f x

Determine the speed at which a Wave Travels What is the speed of a sound wave

that has a wavelength of 2.00m and a frequency of 170.5Hz?

v = (170.5Hz)(2.00m)v = 341 m/s

G

R

A

S

P

f = 170.5Hz = 2.00m

v = ?

v = f x

Determine the speed at which a Wave Travels What is the speed of a sound wave

that has a wavelength of 2.00m and a frequency of 170.5Hz?

v = (170.5Hz)(2.00m)v = 341 m/s

G

R

A

S

P

f = 170.5Hz = 2.00m

v = ?

v = f x

The speed of the sound wave is 341 m/s

Types of Waves

Mechanical WavesElectromagnetic Waves

Mechanical Waves

Can only propagate in a medium

Mechanical Waves

Can only propagate in a medium

How? A disturbance changes the physical shape of the medium and passed onto neighbouring particles

Mechanical Waves

Can only propagate in a medium

How? A disturbance changes the physical shape of the medium and passed onto neighbouring particles

Examples: water waves, sound waves, seismic waves

Electromagnetic Waves

Can propagate in a medium and a vacuum

Electromagnetic Waves

Can propagate in a medium and a vacuum Carry Radiant Energy

Electromagnetic Waves

Can propagate in a medium and a vacuum Carry Radiant Energy

Examples: light waves in space

Electromagnetic SpectrumCategories of electromagnetic

waves Classified by frequency and wavelength

FREQUENCY ENERGY

Electromagnetic Spectrum

Long

Low

Short

High

Electromagnetic SpectrumRadio Waves

Smallest frequency Invisible & transport little energy Example: Radio, Television, Microwaves,

Cellphones

Electromagnetic Spectrum Infrared

Invisible, but feel the warmth emitted Example: Night vision goggles, short-

distance communication (wireless keyboards, remote controls, etc.)

Electromagnetic SpectrumVisible Light

Only electromagnetic waves that can be seen by humans

Together, colours make up white light Example: Photography, movies,

computer screens

Electromagnetic SpectrumUltraviolet Rays (UV)

Invisible to humans Greater frequency, transport more

energy Responsible for suntans, but can cause

cancer Example: sterilization of surgical

instruments, treatments

Electromagnetic SpectrumX-Rays

High frequency Able to travel through media opaque in

visible light Example: baggage inspection,

radiography

Electromagnetic SpectrumGamma Rays

Highest frequency and transports the highest energy

Travel easily through matter Can cause burns, cancer, and genetic

mutations Example: cancer treatment, food

preservation

Homework

Read Textbook pages 92-99Do Workbook pages 49-52