MOTION , FORCES & ENERGY

MOTIONMOTION, , FORCESFORCES& & ENERGYENERGY

TAKS REVIEWTAKS REVIEW

Wake up and smile(:Wake up and smile(:

IPC (5) The student knows

the effects of

on everyday life.

Definitions Anyone?Definitions Anyone?

WAVEWAVE - a transfer of energy, usually through a medium. - a transfer of energy, usually through a medium.

MEDIUMMEDIUM –the substance that a wave moves in. –the substance that a wave moves in.

OSCILLATIONOSCILLATION – to swing or move regularly back and forth. – to swing or move regularly back and forth.

PROPIGATIONPROPIGATION – to transmit or move through a medium. – to transmit or move through a medium.

PERIODIC MOTIONPERIODIC MOTION – motion that is repetitive over a given – motion that is repetitive over a given time interval.time interval.

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

The student is expected to:

5A: demonstrate wave types and their characteristics through a variety of activities such as modeling with ropes and coils, activating tuning forks, and interpreting data on seismic waves.

TYPES OF WAVESTYPES OF WAVES

MECHANICAL WAVESMECHANICAL WAVESNeed a medium to propagate.Need a medium to propagate.

(sound, water, etc.)(sound, water, etc.)

ELECTROMAGNETIC WAVESELECTROMAGNETIC WAVESDo Do notnot need a medium need a medium

to propagate in.to propagate in.(light)(light)

HOW WAVES PROPIGATEHOW WAVES PROPIGATE

Transverse (S-Wave)Transverse (S-Wave)Waves in which the oscillation of theWaves in which the oscillation of themedium is perpendicular to the medium is perpendicular to the propagation of the wave.propagation of the wave.

Longitudinal (P-Wave or Compression)Longitudinal (P-Wave or Compression)Waves in which the oscillation of theWaves in which the oscillation of themedium is parallel to the propagationmedium is parallel to the propagationof the wave.of the wave.

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

Wave CharacteristicsWave Characteristics

Crest & Trough – the maximum displacement of the medium form the equilibrium position

(Compressions & Rarefractions in longitudinal waves).

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

HOW WAVES PROPIGATEHOW WAVES PROPIGATE

Wavelength, Compressions & RarefractionsWavelength, Compressions & Rarefractions in longitudinal waves correspond to in longitudinal waves correspond to

wavelengths, crests & troughs in wavelengths, crests & troughs in transverse waves.transverse waves.

Wave CharacteristicsWave Characteristics

Amplitude – refers to the distance the medium oscillates from equilibrium.

Amplitude indicates the amount of

in the wave.

Wave CharacteristicsWave CharacteristicsWave Period – the time it take for one complete wave cycle to pass by a given point.T = sec/1 cyc

Frequency – the number of cycles that pass by a given point in a given amount of time.

ƒ = cyc/1 sec

Frequency & Period are relatedFrequency & Period are related

!!!!!! WAVE EQUATIONS WAVE EQUATIONS !!!!!!

V = d/tV = d/t velocity = distance / timevelocity = distance / time

V = ƒV = ƒλλ velocity = frequency * velocity = frequency * wavelengthwavelength

Both are measured in meters/second (m/s).Both are measured in meters/second (m/s).

Some ProblemsSome Problems Q1. A sound wave has a Q1. A sound wave has a frequencyfrequency of 3250 Hz of 3250 Hz

and a and a wavelengthwavelength of 0·1 m. What is its of 0·1 m. What is its velocityvelocity??A1. Use A1. Use v = f x lv = f x lv = 3250 x 0·1v = 3250 x 0·1= 325 m/s.= 325 m/s.

Q2. A sound wave travels with a velocity of Q2. A sound wave travels with a velocity of 330 330 m/sm/sand has a frequency of 500 Hz. What is its wavelength?and has a frequency of 500 Hz. What is its wavelength?A2. Use A2. Use l = v ÷ fl = v ÷ f l = 330 ÷ 500l = 330 ÷ 500= 0·66 m.= 0·66 m.

Q3. A wave at sea travels with a velocity of 25 m/s.Q3. A wave at sea travels with a velocity of 25 m/s.If it has a wavelength of 10 m, what is its frequency?If it has a wavelength of 10 m, what is its frequency?A3. Use A3. Use f = v ÷ lf = v ÷ lf = 25 ÷ 10f = 25 ÷ 10 = 2·5 Hz. = 2·5 Hz.

Note - always make sure that you give the units for your answerNote - always make sure that you give the units for your answerand that the units are correct.and that the units are correct.If the wavelength is given in centimeters,If the wavelength is given in centimeters,convert it to meters before doing the calculation.convert it to meters before doing the calculation.

The student is expected to:

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

SUPERPOSITION PRINCIPLE & SUPERPOSITION PRINCIPLE & INTERFERENCEINTERFERENCE

(amplitude addition)(amplitude addition)

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

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

Superposition Principle – The total displacement (amplitude) caused by two or more waves occupying the same space in a medium is equal to the sum of the displacements (amplitudes) of each of the individual waves.

INTERFERENCE PATTERNS FROM INTERFERENCE PATTERNS FROM POINT SOURCE WAVESPOINT SOURCE WAVES

Nodes are areas of destructive interference (in this case, 0 amplitude).

Antinodes are the areas of constructive interference (in this case twice the amplitude).

+ =

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

ReflectionReflection

The bouncing back of waves as they strike a barrier or The bouncing back of waves as they strike a barrier or encounter the boundary of another medium.encounter the boundary of another medium.

Fixed End Reflections are inverted.

Free End Reflections are upright.

Boundary Behavior

Reflections are inverted if the new medium is more dense and upright if the new medium is less dense.

Law of ReflectionLaw of Reflection

Law or Reflection – Angle of incidence = Angle of Reflection

All angles are measured with respect to the normal

Normal – dotted line drawn perpendicular to the surface where the light ray hits the reflecting surface

REFRACTIONThe changing direction of waves as The changing direction of waves as they pass into different mediums.they pass into different mediums.

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. If the new medium is more dense, the wave will slow down and bend toward the “normal.” If it is less dense the wave will speed up, and bend away from the “normal.”

DiffractionDiffractionThe bending of a wave around a barrier, such as an The bending of a wave around a barrier, such as an

obstacle or opening.obstacle or opening.

Occurs when a wave passes an edge, passes through a narrow gap or goes past an object.

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.

ResonanceResonance

a condition that exist when the frequency of a condition that exist when the frequency of a force applied to a system matches the a force applied to a system matches the

natural frequency of vibration of the natural frequency of vibration of the system that causes a dramatic increase in system that causes a dramatic increase in

amplitude. amplitude.

THINK, “CONSTRUCTIVE INTERFERENCE.”THINK, “CONSTRUCTIVE INTERFERENCE.”

Doppler EffectDoppler EffectApparent change in the wave frequency due to motion of Apparent change in the wave frequency due to motion of

wave source and/or observer.wave source and/or observer.

Low Pitch Observed

High Pitch Observed

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,

Sonic BoomSonic Boom

PolarizationPolarization A 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

Problem 2: Wave types & Problem 2: Wave types & characteristicscharacteristics

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.


The pitch of a sound made by plucking a guitar string is determined by the —

A* frequency of the vibration producedB strength of the plucking forceC distance between the stringsD shape of the guitar body


Which of these tools is most useful in identifying the wavelengths of visible light?

F Convex lensG SpectroscopeH MicroscopeJ Concave mirror


Which of the following would explain why this film works with a reduced amount of light?

A The film reflects long wavelengths of light efficiently.

B Fewer silver halide granules are present in the film.

C The film refracts brighter light.D The photochemical reaction can occur in

lower intensity light.


Which wave has the greatest velocity?


At 0°C sound travels through air at a speed of 330 m/s. If a sound wave is produced with a wavelength of 0.10 m, what is the wave’s frequency?

F 0.0033 HzG 33 HzH 330 HzJ* 3300 Hz

Problem 8: Wave Problem 8: Wave InteractionsInteractions

The diagram shows waves approaching a barrier. Which pattern will be formed after the waves pass through the opening in the barrier?

Problem 9: Wave InteractionsProblem 9: Wave Interactions

Polarized sunglasses are useful because –F. They are dark and don’t allow as much

light to come through.G. They reflect much of the light from their

surfaces.H. They filter out the horizontal transverse

waves in light while allowing only the vertical waves to get to the eyes.

J. They both diffract and refract light.


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


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


When trying to spear a fish in water, a personneeds to take into account the way light bendsas it moves from water into air. The bending oflight as it passes from one medium intoanother is known as —F reflectionG* refractionH diffractionJ polarization


One tuning fork is struck and placed next to an identical fork. The two forks do not touch. The second tuning fork starts to vibrate because of —

-or-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?

F interferenceG the Doppler effectH* resonanceJ standing waves


What provides evidence that white light is actually a combination of all the colors?

A. An array of colors is seen when white light has moved through a prism.

B. The wavelengths of colored light are different.

C. All colored light refracts the same amount.

D. All colored light has the same wavelength.

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