2011_ TAKS _Physics _ Review_64-124

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Waves A wave is a disturbance that travels from one point to another transporting or transmitting energy . One way to categorize waves is on the basis of their ability or inability to transmit energy through empty space (also known as a vacuum).

Electromagnetic Waves:

Electromagnetic Waves Electromagnetic waves can transmit energy through a vacuum . Light is a good example of this kind of wave because it travels through space to reach earth.

Mechanical Waves:

Mechanical Waves Mechanical waves require a medium to travel . Sound is a good example because it cannot travel through a vacuum. Other mechanical waves include slinky waves, water waves, stadium waves, seismic waves, and jump rope waves .

Transverse vs. Longitudinal:

Transverse vs. Longitudinal Another way to categorize waves is based on the movement of the particles that make up the wave relative to the direction of the wave as a whole.

Transverse Waves:

Transverse Waves Transverse waves have particles that move perpendicular to the direction of the wave. When the particles move up and down the wave is moving from side to side.

Longitudinal Waves:

Longitudinal Waves Longitudinal waves have particles that move paralle l to the direction of the wave. When the particles move side to side the wave is also moving side to side.

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Compressions – in which particles are closer together Rarefactions – in which particles are farther apart .

Parts of a Wave:

Parts of a Wave Crest – highest point of a wave Trough – lowest point of a wave Amplitude – height from equilibrium line to crest Wavelength – distance between 2 crests or troughs Frequency – number of complete wavelengths that pass a point in 1 second . Period – time it takes one complete wavelength to pass a point.

Label Your Wave:

Label Your Wave Crest Trough { Amplitude { Wavelength

Wave Interactions:

Wave Interactions Reflection – when a wave bounces off barriers in a regular way. Reflection changes when the surface changes. A smooth surface will provide a more clear reflection ( specular ) than an rough or irregular surface. (diffuse)

Wave Interactions:

Wave Interactions Refraction – the speed and direction a wave travels can change due to the medium it is passing through. Light waves bend when they move from air to water .

How We See Color:

How We See Color Visible light is an electromagnetic wave. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all waves are seen together, they make white light.

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The color an object appears depends on the wavelength of light it reflects. - When an object is hit with white light, that object will absorb all the wavelengths EXCEPT the wavelength of the color that object appears. - White objects reflect all colors. - Black objects absorb all colors. A blue book reflects blue light and absorbs all other light.

What color does a green leaf appear when red light shines on it? Why? :

What color does a green leaf appear when red light shines on it? Why? The green leaf appears black as there is no green light to reflect back.

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A red flower would appear red when white light shines on it because it reflects back the red component of the white light (white light is made up of all seven colors). What color does a red flower appear when white light shines on it? Why?

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Resonance – when one object vibrates causing a second object at the same frequency to also vibrate . Tuning forks are an example you may see in a lab (or music hall) . Loud music making the rest of your car vibrate is another example of resonance. Wave Interactions

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Interference – when waves interact as they meet. Interference can be constructive or destructive . Constructive interference – when the sum of the two waves creates an amplitude larger than the waves were before the interaction. Destructive interference – when the sum of the two waves creates an amplitude smaller than the waves were before the interaction. (This interference can result in a wave that seems to flatten out) Wave Interactions

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Destructive Interference

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Constructive Interference

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Diffraction – the bending of light waves around an object in it's path. This is due to light's being a wave, and how it spreads out from the source, not in straight lines, but in curved waves. Wave Interactions All waves diffract – not just light waves. Water waves spread out beyond a narrow gate. Sound waves bend around a tree.

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B. 29.

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Bending because medium changes is refraction . 30.

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A. 31.

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D. Waves bouncing back is called reflection. 32.

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A . Pitch is frequency . Loudness is amplitude . 33.

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Use formula chart v = f * λ V = 1 m x 2 Hz = 2 m/s V = 2 m x 8 Hz = 16 m/s V = 3 m x 3 Hz = 9 m/s V = 4 m x 1 Hz = 4 m/s SKIP

Seismic Waves:

Seismic Waves Seismic waves – waves of energy that travel through the earth . These waves are most often discussed in connection with earthquakes or movement of the earth’s crust/tectonic plates .

Seismic Waves:

Seismic Waves - The strength of seismic waves is measured using a seismograph - When an earthquake occurs, the point of origin is the epicenter . - Seismic waves can be felt miles away from the origin, and will feel weaker the further away they are.

Seismic Waves:

Seismic Waves Where is the origin of the seismic wave? Where will the waves be felt the strongest? Where will the waves be felt the weakest? A B C A A (then B) C

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A surface wave generated by an earthquake was recorded at Seismic Station 1. Forty seconds later the same wave was recorded at Seismic Station 2. What accounts for the time difference? A. The origin of the wave is closer to Seismic Station 1. B. The speed of the wave decreases with distance. C. The wavelength is longer at Seismic Station 2. D. The wave frequency increases when the wave passes through soil. 35.

Acoustic Waves (Sound Waves):

Acoustic Waves (Sound Waves) Sound waves are mechanical because they must travel through mediums including solids, liquids , and gases . - The speed the sound waves travel depend on the medium and its properties.

Acoustic Waves:

Acoustic Waves Certain materials reflect sound waves, making the noise level increase. - Sound waves bounce off surfaces including floors, ceilings and walls. - Specifically tile, cement, wood all create a loud environment.

Acoustic Waves:

Acoustic Waves Other materials absorb sound waves, making the noise level decrease. - Special floor and ceiling tiles decrease sound wave reflection. - Specifically carpet, fabric, drapes all help to create a quieter environment. ** Sound travels faster in water and slower in air . Sound travels about 343 m/s in air (768 mph), and 4 times faster in water.

Electrical Energy:

Electrical Energy Electricity – the movement of electrons along a path. Electric circuit diagram – a set up in which the components involved in creating electricity are represented by a variety of symbols . Circuits that are closed allow the flow of electricity while circuits that are open cause the flow to stop.

Components of a simplified circuit include::

Components of a simplified circuit include: 1. Battery – Source of power (= volts) 2. Wire – Connects all other components 3. Light bulb (lamp) – Powered by circuit – brightness indicates electricity flow 4. Switch – Turn on or off to create closed or open circuit 5. Resistor – Decreases flow of electricity (reduces current = amps)

Types of Circuits:

Types of Circuits There are 2 types of circuits: 1) Series circuits are simple. There is only one path for the current to travel. - If the circuit is opened by any means, the electricity will not flow to any of the rest of the parts. - This means that we rarely see circuits in series because they are considered impractical for everyday life

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2) Parallel circuits provide multiple (more than one) paths for the current to travel. - If the circuit is opened at one point, the electricity has other paths it can choose to allow flow to continue. - This means that most circuits are parallel because this provides more efficiency in large scale electrical set-ups

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Parallel Series

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D. Parallel circuit 36.

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Q R S T Which switch, if opened, will cause the light bulb to stop glowing? Every loop from battery through light bulb must go through Q. 37.

Heat Transfer:

Heat Transfer Conduction – Transfer of heat by direct contact . Conduction takes place in solids . - A solid pot on a hot stove conducts heat by touching the heat source . Convection - Heating by circulating fluids . Fluids include both liquids and gases . - Air currents and weather patterns are caused by convection . - The water boiling inside a pan is convection current. Stirring and mixing fluids transfers heat.

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Radiation - electromagnetic waves that can travel through a vacuum to reach an object. No molecular contact is needed. - The sun sending heat and light is radiation. (electromagnetic radiation) - Feeling the heat from a fire without directly touching it is another example of radiation. Heat Transfer

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Solids are unable to transfer heat by fluid motion (which is called convection ) . 38.

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The transfer of heat by the movement of air currents in Earth’s atmosphere is an example of – A. Conduction B. Convection C. Radiation D. Fusion 39.

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A. Conduction – physical contact. Touch the wooden door before touching the metal doorknob. 40.

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C. Air currents are caused by convection. 41.

Energy Sources:

Energy Sources Energy can be generated through many sources. Each source has both pros and cons to be considered before use.

Energy Sources:

Energy Sources Solar - energy from the sun . - Comes in the form of solar panels or photovoltaic cells (direct transfer of energy from sunlight to electricity)

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Wind – energy from wind (air currents) “Wind farms” use large amounts of land to place windmills Hydroelectric – energy from water that powers turbines. Machinery or dams are placed along bodies of water such as rivers. Energy Sources

Energy Sources:

Energy Sources Fossil fuel – energy from non-renewable = limited sources Includes gasoline/oil/ petroleum, coal, natural gas . Batteries – energy stored in cells for later use Includes disposable and rechargeable .

Energy Sources:

Energy Sources Nuclear – energy from reactions including splitting or combining of atoms. Creates radioactive waste, but high amounts of energy

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More nuclear power would reduce dependence upon imported oil. Building new nuclear power plants in the U.S. has been politically difficult since Three Mile Island (1979) and the Chernobyl disaster (1986). The March 2011 Japanese earthquake and tsunami has resulted in radiation leakage from the Fukushima Daiichi nuclear plant.

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B. Solar cells 42.

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C. Advantage: solar power plants produce fewer pollutants. Coal has advantages of continuous operation and controlled/variable production. 43.

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C. Can be used many times. 44.

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D. Photovoltaic cell: photo = sun, volt = electricity. 45.

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B. Fossil Fuels 46.

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A. Cloudy skies 47.

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In West Texas and Southern California, high winds drive turbines that generate electricity. One advantage that wind energy has over energy generated from solar cells is that wind energy - A. Is plentiful everywhere B. Can be generated at night C. Produces cleaner energy D. Is free of environmental hazards 48.

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Heavy metals such as mercury, cadmium, and nickel are often found in landfills and occasionally leach into rivers, lakes, and other bodies of water. Such heavy metals are toxic to wildlife and to humans. Which of the following sources of environmental contamination is most often associated with these heavy metals? A. Batteries B. Plastics C. Automobile exhaust D. Tobacco smoke 49.

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