Definitions WAVE - a transfer of energy, usually through a

medium.

MEDIUM –the substance that a wave moves in.

OSCILLATION – to swing or move regularly back and forth.

FYI - In a wave, the energy moves through the medium, BUT THE OBJECT STAYS PUT (although it may oscillate).

Wave types

MECHANICAL WAVESNeed a medium to move through.

Ex: sound, water, etc.

ELECTROMAGNETIC WAVESDo not need a medium.

Ex: light

How Waves MoveTransverseParticles in the medium move perpendicular to the direction of the wave.

Longitudinal (Compressional)Particles in the medium move parallel to the direction of the wave.

Transverse & Longitudinal Waves in Action!!! (link)

Wave CharacteristicsCrest & Trough – the highest & lowest point, respectively, of a transverse wave. (Compressions & Rarefractions in longitudinal waves).

Wavelength – the length of one complete wave cycle. (crest to crest, trough to trough)

Wave Characteristics

Amplitude – the height measured from the resting line.

Amplitude indicates the amount ofin the wave.

Frequency – the number of waves that pass a given point in one second. Measured in Hertz (Hz). Frequency determines the pitch of a sound.

Wave Characteristics

Wave SpeedTo calculate wave speed/velocity (v), we need

1. Frequency (f) in Hertz (Hz) &

2. Wavelength (λ) in meters (m)

Our formula is: Speed = frequency x wavelength

v =f λThe units for speed are usually m/s.

Problem 1: Wave types &

characteristics

Which illustration best demonstrates compression waves?

Problem 2: Wave types & characteristics

Which of the following is not true about a wave?

A. Its energy increases as its amplitude increases.

B. Its frequency increases as its wavelength decreases.

C. Its velocity is equal to its frequency times its wavelength.

D. It transfers the particles of the medium along with the energy created by the disturbance.

Problem 3: Wave types & characteristics

Which wave has the greatest velocity?

V = ƒλA. v = (2 Hz)(1 m) = 2 m/sB. v = (8 Hz)(2 m) = 16

m/sC. v = (3 Hz)(3 m) = 9 m/sD. v = (1 Hz)(4 m) = 4

m/s

The student is expected to:

5B: demonstrate wave interactions including interference, polarization, reflection, refraction, and resonance within various materials.

Wave Interactions

Constructive Interference – The addition of two or more overlapping waves that produced a wave of increased amplitude.

Destructive Interference – The addition of two or more overlapping waves that produces waves of decreased amplitude.

INTERFERENCE PATTERNS FROM POINT SOURCE WAVES

Nodes are areas of destructive

interference (zero amplitude).

Antinodes are the areas of constructive

interference (2x amplitude).

+ =

Two point source waves. Light rings are wave crests, dark rings are troughs.

ReflectionThe bouncing back of waves as they strike a

barrier or encounter the boundary of another medium.

REFRACTIONAs waves pass into different mediums, they travel at different speeds and bend.

Check this out! (link)

When a wave enters a new medium, the change in density of a new medium causes the wave to travel at a different speed.

DiffractionThe bending of a wave around a barrier,

such as an obstacle or opening.

None of the properties of a wave are changed by diffraction. The wavelength, frequency, period and speed are same before and after diffraction.

The only change is the direction in which the wave is traveling.

ResonanceWhen the frequency of a force applied to a

system matches the natural frequency of vibration of the system and causes a

dramatic increase in amplitude.

CONSTRUCTIVE INTERFERENCE!

PolarizationA method of reducing the number of planes

that light waves are vibrating in.

Polarizing sun glasses reduce glare by blocking light waves vibrating in a certain

direction.

http://www.polarization.com/water/glare-tacho_movie.gif

Doppler EffectApparent change in the wave frequency (and pitch) due

to motion of wave source and/or observer.

Low pitch

heard

the wave length behind the object

appears to lengthen -

the wave length in front of the object appears to decrease.

As sound is emitted from a moving object,

High pitch heard

Problem 4: Wave Interactions

Polarized sunglasses are useful because –

A. They are dark and don’t allow as much light to come through.B. They reflect much of the light from their surfaces.C. They filter out the horizontal transverse waves in light while allowing only the vertical waves to get to the eyes.D. They both diffract and refract light.

Problem 5: Wave Interactions

Dolphins and bats use echolocation to hunt prey. They determine the distance to their prey by sending sound waves out and measuring the time it takes for the sound wave to return. This demonstrates the ability of sound waves to

A. RefractB. InterfereC. ReflectD. Polarize

Problem 6: Wave Interactions

This graph shows the absorption spectrum for a certain pigment molecule. To a human, this pigment would most likely appear —

A. blueB. greenC. yellowD. orange

Problem 7: Wave Interactions

A guitar player is seated next to a piano. The piano player strikes an E key on the piano. The guitarist reports that this causes the E string on his guitar to vibrate. What is the name of this phenomenon?

A. interferenceB. the Doppler effectC. resonanceD. standing waves