Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a...

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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).

Transcript of Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a...

Page 1: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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).

Page 2: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

Wave types

MECHANICAL WAVESNeed a medium to move through.

Ex: sound, water, etc.

ELECTROMAGNETIC WAVESDo not need a medium.

Ex: light

Page 3: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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)

Page 4: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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)

Page 5: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

Wave Characteristics

Amplitude – the height measured from the resting line.

Amplitude indicates the amount ofin the wave.

Page 6: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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

Page 7: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 8: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

Problem 1: Wave types &

characteristics

Which illustration best demonstrates compression waves?

Page 9: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 10: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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

Page 11: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

The student is expected to:

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

Page 12: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 13: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 14: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

ReflectionThe bouncing back of waves as they strike a

barrier or encounter the boundary of another medium.

Page 15: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 16: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 17: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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!

Page 18: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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

Page 19: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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

Page 20: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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.

Page 21: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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

Page 22: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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

Page 23: Definitions WAVE - a transfer of energy, usually through a medium. MEDIUM –the substance that a wave moves in. OSCILLATION – to swing or move regularly.

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