What are wavesWhat are waves

Waves are an important part of Waves are an important part of the Earth, and not just in the the Earth, and not just in the

water.water.

What is a wave?What is a wave?

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

What is energy?What is energy? In science, we define In science, we define

energy as the ability to do energy as the ability to do work.work.

In the photo Ms. Turner is In the photo Ms. Turner is being moved around by being moved around by the energy of the wave. the energy of the wave. When she is being When she is being pushed around by the pushed around by the waves the energy in the waves the energy in the waves is performing work waves is performing work by moving her around in by moving her around in the surf. the surf.

What carries a wave?What carries a wave? Many waves require something to Many waves require something to

carry them. carry them. Any substance which carries a wave Any substance which carries a wave

is a is a ““mediummedium””.. Some examples of mediums are:Some examples of mediums are:

Gases, Air, Liquids, Water, and Gases, Air, Liquids, Water, and Solids.Solids.

Waves that require a medium to Waves that require a medium to travel are called travel are called ““mechanical wavesmechanical waves””..

What causes waves?What causes waves? Waves are caused when a Waves are caused when a

source of energy causes a source of energy causes a medium to vibrate. medium to vibrate.

A vibration is a repeated back A vibration is a repeated back and forth or up and down and forth or up and down motionmotion

A moving object can transfer A moving object can transfer energy to a nearby medium energy to a nearby medium to produce a wave.to produce a wave.

A boat moving through the A boat moving through the ocean (a medium) creates a ocean (a medium) creates a wave.wave.

The three types of wavesThe three types of waves

Waves are Waves are classified by how classified by how they move.they move.

Waves types:Waves types:

Transverse waves.Transverse waves.

Longitudinal waves.Longitudinal waves.

Surface waves.Surface waves.

Transverse wavesTransverse waves Transverse waves: Transverse waves:

move the medium at move the medium at right angles to the right angles to the direction of the direction direction of the direction of wave movement.of wave movement.

An example would be An example would be the waves of a rope. the waves of a rope.

As the medium moves As the medium moves up, the wave moves up, the wave moves forward.forward.

Lets Draw a Diagram!Lets Draw a Diagram!

Longitudinal wavesLongitudinal waves

In longitudinal waves the medium particles In longitudinal waves the medium particles move parallel (in the same direction) as move parallel (in the same direction) as the wave is traveling.the wave is traveling.

An example would be a spring.An example would be a spring. Compressions: areas which the coils in a Compressions: areas which the coils in a

spring are close together. spring are close together. Rarefactions: areas which the coils of a Rarefactions: areas which the coils of a

spring are spread out.spring are spread out. Lets draw another diagram!Lets draw another diagram!

Surface wavesSurface waves A combination of two A combination of two

mediums working mediums working together to produce together to produce waves. waves.

An example would be An example would be water and air combining water and air combining to produce waves on the to produce waves on the ocean.ocean.

The air is applying energy The air is applying energy to the water which alters to the water which alters the wave direction and the wave direction and the intensity of the wave.the intensity of the wave.

Properties of wavesProperties of waves Amplitude: is maximum distance the particles of Amplitude: is maximum distance the particles of

the medium carrying the wave move away from the medium carrying the wave move away from their rest positions. The amplitude is a measure their rest positions. The amplitude is a measure of how much a particle in the medium is of how much a particle in the medium is disturbed by the wave. disturbed by the wave.

Wavelength: the distance between two crests of Wavelength: the distance between two crests of two waves.two waves.

Frequency: the number of waves that pass a Frequency: the number of waves that pass a given point in a certain amount of time. given point in a certain amount of time. (frequency is measured in hertz, Hz).(frequency is measured in hertz, Hz).

Speed: how far a wave travels in one unit of Speed: how far a wave travels in one unit of time.time.

Speed, Wavelength, and frequency Speed, Wavelength, and frequency relationships.relationships.

Speed = Wavelength x FrequencySpeed = Wavelength x Frequency When you have two quantities of the formula you When you have two quantities of the formula you

can calculate the third.can calculate the third. Frequency = Wavelength / Speed Frequency = Wavelength / Speed Wavelength = Speed / FrequencyWavelength = Speed / Frequency Sample problem: The speed of a wave on a rope Sample problem: The speed of a wave on a rope

is 50 cm/second and the wavelength is 10 cm. is 50 cm/second and the wavelength is 10 cm. What is the frequency?What is the frequency?

Frequency = 50 cm/s / 10 cmFrequency = 50 cm/s / 10 cm 50 / 10 = 5 (5 per second) or 5 Hz 50 / 10 = 5 (5 per second) or 5 Hz

More sample problemsMore sample problems

A wave has a wavelength of 5 mm and a A wave has a wavelength of 5 mm and a frequency of 2 Hz. At what speed does the frequency of 2 Hz. At what speed does the wave travel?wave travel?

The speed of a wave on a guitar string is The speed of a wave on a guitar string is 100 m/s and the frequency is 1000 Hz. 100 m/s and the frequency is 1000 Hz. What is the wavelength of the wave?What is the wavelength of the wave?

Answers to the sample problemsAnswers to the sample problems A wave has a wavelength of 5 mm and a A wave has a wavelength of 5 mm and a

frequency of 2 Hz. At what speed does the frequency of 2 Hz. At what speed does the wave travel?wave travel?

Answer: speed = wavelength x FrequencyAnswer: speed = wavelength x Frequency 5(mm) x 2 (Hz) = 10 mm per second5(mm) x 2 (Hz) = 10 mm per second The speed of a wave on a guitar string is 100 The speed of a wave on a guitar string is 100

m/s and the frequency is 1000 Hz. What is the m/s and the frequency is 1000 Hz. What is the wavelength of the wave?wavelength of the wave?

Answer: wavelength = speed/FrequencyAnswer: wavelength = speed/Frequency 100 (m/s) / 1000 (Hz) = 0.1 meter100 (m/s) / 1000 (Hz) = 0.1 meter

What are electromagnetic waves?What are electromagnetic waves? Electromagnetic waves do Electromagnetic waves do

not require a medium to not require a medium to transfer energy.transfer energy.

These waves carry both These waves carry both electrical and magnetic electrical and magnetic fields.fields.

These waves carry a These waves carry a electrical field vertically and electrical field vertically and the magnetic field is carried the magnetic field is carried horizontally.horizontally.

The energy carried by The energy carried by electromagnetic waves is electromagnetic waves is called electromagnetic called electromagnetic radiation.radiation.

These waves travel at the These waves travel at the speed of light.speed of light.

What does the electromagnetic What does the electromagnetic spectrum look like?spectrum look like?

The longest wavelengths and the lowest frequencies The longest wavelengths and the lowest frequencies waves are on the leftwaves are on the left

The shortest wavelengths and the highest frequency The shortest wavelengths and the highest frequency waves are on the right.waves are on the right.

Notice how the light we see as a species is in the Notice how the light we see as a species is in the middle of the spectrum.middle of the spectrum.

What are the rays of the electromagnetic What are the rays of the electromagnetic spectrumspectrum

Radio waves – used to broadcast both AM and FM Radio waves – used to broadcast both AM and FM stations. These are the longest wavelengths.stations. These are the longest wavelengths.

Microwaves – shorter wavelengths, used in microwave Microwaves – shorter wavelengths, used in microwave ovens to cook.ovens to cook.

Infrared rays – used by heat lampsInfrared rays – used by heat lamps Visible light – the Visible light – the ““colorscolors”” that we can see. that we can see. Ultraviolet rays – can cause cancer or damage the Ultraviolet rays – can cause cancer or damage the

eyes.eyes. X-rays – used to make images of bones.X-rays – used to make images of bones. Gamma rays – these waves have the shortest Gamma rays – these waves have the shortest

wavelengths, but carry the greatest amount of energy. wavelengths, but carry the greatest amount of energy. Used in cancer treatments (radiation therapy) Used in cancer treatments (radiation therapy)