PHYSICS UNIT-WAVES, GRAVITY, AND ENERGY

WAVE PROPERTIES

WAVE PROPERTIES-WAVELENGTH AND AMPLITUDE

The wavelength is the distance from crest to crest or from trough to trough.

The wavelength is the distance between two corresponding parts of a wave.

The greater the wavelength the less energy the wave has.

Measuring Wavelength

WAVE PROPERTIES-WAVELENGTH AND AMPLITUDE

Think about big waves usually come with a higher frequency (time between crest) and smaller wavelengths. (distance between crests)

WAVE PROPERTIES-WAVELENGTH AND AMPLITUDE

Amplitude is the maximum distance the particles of the medium carrying the wave move away from their resting position.

Sound waves that have smaller amplitudes are softer sounds.

WAVELENGTH QUESTION

Which one of the waves would wave C look like if you decreased it’s wavelength?

A

AMPLITUDE QUESTION

What would line A look like if you increased it’s amplitude?

B

FREQUENCY QUESTION

What would wave D look like if you increased its frequency?

B

WAVE SIMILARITIES QUESTION

How are wave A and wave C similar? A.  both have the same frequency   B.  both have the same amplitude   C.  both have the same wavelength   D.  wave C has half the amplitude of wave A

Correct Answer is B

WHAT IS A WAVE?

A wave is a disturbance that transfers energy from place to place.

Many waves require something to travel through.

Water waves travel along the surface of the water. Sound waves travel through air.

The material through which a wave travels is called a medium.

WAVE PROPERTIES-PERIOD AND FREQUENCY OF A WAVE

The period of a wave is the time it takes to go from one crest to another. Period is normally measured in seconds.

Frequency is the number of crest passages for a specific amount of time. For example how many crests can pass in one minute.

Short wavelength=High Frequency

Long wavelength=Low Frequency

THE GREATER THE AMPLITUDE THE GREATER THE ENERGY WAVE

Think of amplitude in terms of a wave on water. The bigger (taller) the wave the more the boat moves up and down because of greater amplitude! 

It takes energy to move a boat in the water. But you'll notice the boat stays in the same place, it only goes up and down. 

MEDIUM MOVEMENT WHEN A WAVE PASSES

So when a wave passes through a medium (like water) the medium travels forwards and backwards parallel to the direction of the movement.

WAVES PASS THROUGH MEDIUMS

The same thing happened when you made a paper cup telephone when you were a kid. Sound waves passes down the string which was the medium. The sound waves were then amplified by the cup.

DEFINITION OF A WAVE

The definition of a wave is the transfer of energy through matter or space.

Smaller waves cause less movement because they have less energy - or a smaller amplitude. Larger waves like a tsunami hold a huge amount of energy. That is why they are so damaging.

Wave Computer Demo Wave Fire Demo Tim and Moby Wave Video

DIFFERENT MEDIUMS WAVES CAN TRAVEL THROUGH

So we have learned so far that waves transfer energy through various mediums.

Sound, Light, Earthquake Waves, and Heat all travel by waves through various mediums.

DIFFERENT MEDIUMS WAVES CAN TRAVEL THROUGH

Seismic Waves or Earthquake waves travel through various mediums

Remember primary waves or P waves travel through solids and liquids

Remember secondary waves or S waves can only travel through solids.

DIFFERENT MEDIUMS WAVES CAN TRAVEL THROUGH

What mediums does heat travel through well.

If I heat up something solid can I feel it?

If I heat up something liquid does it get warm?

If I start a camp fire and sit around it can I feel it?

WHAT MEDIUMS DO SOUND WAVES TRAVEL THROUGH?

Sound waves travel through the air.

Think about it when you need to tell somebody something from far away you might shout. By shouting you send out sound waves which can travel a great distance through the air.

Sound can travel through all forms of matter-solids, liquids, gasses, and plasma.

Sometimes these forms of matter can muffle or diminish the sound but if it is loud enough it can travel through it.

WHAT MEDIUMS DO SOUND WAVES TRAVEL THROUGH?

Sound waves can travel through solids.

Examples are knocking on a door and putting your ear down on a railway track to hear if a train is coming.

WHAT MEDIUMS DO LIGHT WAVES TRAVEL THROUGH?

Light, for example, can travel through air, water, glass, and even empty space (and other things as well).

Light does not need a medium to travel. Light waves are different than sound waves because they require no medium for travel.

ELECTROMAGNETIC SPECTRUM

Red has a bigger wavelength then Violet colors. The bigger the wavelength the less energy it is carrying.

ELECTROMAGNETIC SPECTRUM Gamma Ray’s have more energy because they shorter

wavelengths. Violet is the color with the most energy! Electromagnetic Spectrum Video

PRISMS-BREAKING UP LIGHT

A prism can be used to break light up into its constituent spectral colors (the colors of the rainbow)

A Prism bends the white light different amounts to create light with various wavelengths. (colors)

Because colors like violet and blue have shorter wavelengths their wavelength has to be bent the most by the prism.

PRISMS-BREAKING UP LIGHT

If colored light falls on a prism it changes the direction of the light but not the color.

For example if red light falls on this prism it is still red light but it is refracted into a straight line.

SO HOW DOES A PRISM WORK?

A prism separates white light into rainbow colors by taking wavelengths of white light and bending them different amounts.

Once again violet has to be bent the most because of it’s short wavelength.

So remember that white light can be separated into all the various colors.

SO HOW DOES A PRISM WORK?

So what would happen if yellow light shown on a prism?

It would simply change the direction of the light but not the color of it.

Only white light is separated into various colors.

Light and Energy Video

DECREASING SOUND

When you whisper you have decreased the amplitude of your sound wave.

The sound wave can transfer smaller amounts of energy.

Sound is transferred forward and backward parallel to the direction of the wave.

TUNING FORKS

Pitch represents the perceived fundamental frequency of a sound.

Remember frequency is the number of crest passages for a specific amount of time.

Tuning Forks resonate at a certain pitch or frequency. The bigger the tuning fork the softer the pitch.

Also remember since pitch is measuring frequency. The smaller the pitch=the lower the frequency.

PLAYING WITH PITCH

If you lower the amount of water in a glass it will have a higher pitch if you were to strike the glass with a metal object.

The more water that is there the lower the pitch will be.

The more water available in the glass the less it will vibrate creating a lower pitch.

The less water available in the glass the more it will vibrate creating a higher pitch.

Tim and Moby on Sound Waves

THUNDER AND LIGHTNING

Have you ever watched Lightning and listened to the Thunder at night?

Why do you see the Lightning first then hear the Thunder after?

Lightning or light travels quicker through the medium of air then does sound or thunder waves.

THE SPREAD OF ENERGY

Energy radiates outward from an energy producing source.

Think of the sun. Energy originates from the inside as Hydrogen is converted into Helium. It then radiates from the inside to the outside and then beyond.

Don’t think of it in a straight line but more so a circular pattern that travels circularly outward from the center of the source.

DOPPLER EFFECT

The apparent change in frequency as a wave source moves in relation to the listener is called the Doppler Effect.

Even though a police siren has a constant frequency it doesn’t sound that way to a listener.

As the car moves toward you, the pitch of the siren is higher. As the goes by and moves away the pitch drops. But the frequency of siren is not really changing.

THE SPREAD OF ENERGY

Also notice in this picture how sound travels from an energy source.

SPREAD OF ENERGY QUESTION

Which of these is an example of how energy spreads from an energy-producing source?

A.  a glass of water spilled on the floor   B.  light from a candle   C.  a laser beam reflected by a mirror   D.  a flame burning a piece of paper

Answer B is Correct

TRANSFER OF HEAT ENERGY-CONDUCTION

Conduction is heat transfer from one particle of matter to another particle of matter. This is done through. direct contact of heat

Examples a metal spoon sitting in a hot pot of water or heating up a horseshoe in fire or a pancake being cooked on a griddle.

TRANSFER OF HEAT ENERGY-CONVECTION

Convection is the upward movement of energy or heat within a fluid liquid or gas.

Earlier this year with talked about convection currents within the mantle causing continental drift or the shifting of plate tectonics.

When your heating up water it comes up to the surface and bubbles releasing it’s energy then sinking down to the bottom again.

TRANSFER OF HEAT ENERGY-RADIATION

Radiation is the transfer of energy or heat by electromagnetic waves.

Radiation from the sun helps warm the earth.

Radiation can be felt from fires and other heat sources.

TRANSFER OF HEAT PICTUREHeat Transfer Module

MASS AND WEIGHT-THEY ARE NOT THE SAME

Sometimes people use the words weight and mass to mean the same thing. This, however, is not accurate. Weight is related to mass, but it is not the same.

Scientists measure weight using a unit called the newton (N). Usually we refer to weight in pounds and ounces.

MASS AND WEIGHT-THEY ARE NOT THE SAME

Weight is a measure of how gravity affects the mass of an object.

Your weight can change depending upon the gravity. So you don’t weigh the same on another planet.

Weight on Other Worlds Website

MASS AND WEIGHT-THEY ARE NOT THE SAME

Mass is the amount of matter in an object and does not change with location. Scientists measure mass using a unit called the gram (g).

If an object is moved to a location of greater gravitational force, such as Saturn, its weight will increase, but mass still remains the same.

Age on Other Planets

MASS AND WEIGHT-THEY ARE NOT THE SAME

The only way to change the mass of an object is to take away part of the object or add to it.

We can measure mass with a triple beam balance or an electronic science scale.

MASS AND WEIGHT-THEY ARE NOT THE SAME

Weight is measured with either a scale or a spring scale.

SO YOUR WEIGHT CAN CHANGE DUE TO GRAVITY…..WELL WHAT CAN CHANGE GRAVITY?

Gravity acts between all objects in the universe.

Any two objects in the universe, without exception, attract each other.

This means that you are not only attracted to the Earth, but you are also attracted to all the other objects around you!

Earth and the objects around you are attracted to you as well.

SO YOUR WEIGHT CAN CHANGE DUE TO GRAVITY…..WELL WHAT CAN CHANGE GRAVITY?

So why don’t you notice that the objects around you are pulling on you?

The reason is that the strength of the force depends on the masses of the objects involved.

The force of gravity is much greater between you and Earth than between you and your book.

SO YOUR WEIGHT CAN CHANGE DUE TO GRAVITY…..WELL WHAT CAN CHANGE GRAVITY?

So what else besides mass effects gravity?

Gravity is also effected by distance from the object.

For example if you travel to the moon you no longer feel the gravitational pull of earth but you now feel the gravitational pull of the moon. (which is 1/6 that of Earth’s)

SO YOUR WEIGHT CAN CHANGE DUE TO GRAVITY…..WELL WHAT CAN CHANGE GRAVITY?

So remember that gravity determines your weight which is measured in Newtons.

Gravity is determined by the mass of an object (such as a planet) and your distance to that object.

Wile E. Coyote constantly defies gravity before being punished by it.

SO YOUR WEIGHT CAN CHANGE DUE TO GRAVITY…..WELL WHAT CAN CHANGE GRAVITY?

So if you want to decrease the amount of gravity effecting a certain item what do you do?

You can increase the distance between yourself and that item (you can leave the Earth so there is greater distance between you and the earth)

Or you can decrease the amount of matter or mass of either of the two objects.

Tim and Moby on Gravity

GRAVITY IS LARGER WITH LARGE MASS ITEMS

Isaac Newton discovered that large masses have more gravity then small masses.

Evidence that supports this is the sun (which is larger than the planets) holding planets in orbit with it’s gravity.

MASS VS. WEIGHT

MASS Measures the

amount of matter in an object

Always constant Measured with a

balance. Expressed in

kilograms, grams, or milligrams.

WEIGHT Measures the

gravitational force on the object

Varies depending on gravity

Measured with a spring scale

Expressed in Newtons (N)

GRAVITY QUESTION

In which of the situations would a given weight remain the same?

A.  on Earth and on the moon   B.  on Earth and in a space station orbiting

above the Earth   C.  in Utah and in Wyoming at the same

altitude   D.  on Earth and Mars

The Correct Answer is C

GRAVITY QUESTION #2

Which of the following best restates how Earth’s gravitational force on an object depends upon the distance of the object from Earth?

A.  the closer an object is to Earth, the less the attraction of gravity.  

B.  the further two objects are from one another the greater the attraction.  

C.  Earth’s gravitational force is proportional to its distance from the Sun.  

D.  the further an object is from Earth, the less affect Earth’s gravity has on it.

Correct Answer is D