Two types of_waves
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Transcript of Two types of_waves
Essential Question?
• How does a wave transfer energy?
Waves• Wave – a disturbance that carries energy
through matter or space• For an example; • Ocean waves disturb water and transfer energy
through• During an earthquakes, energy transferred in
powerful waves that travel through the earth• Light is a type of wave that can travel through an
empty space from one place to another.
Wave – a disturbance that carries energy through matter or space
Mechanical waves –require a medium to travel through
Medium – something that something travels through
Sound travels through air, therefore, air is the medium.
Waves in a pond travel through water, therefore, water is the medium.
Waves1. You have learned how Newton's laws of
motion and principles of conservation of energy govern the behavior of particles.
2. These laws and principles also govern the motion of waves.
3. There are many types of waves that transmit energy even the ones you cannot see.
• Mechanical Waves - A mechanical wave is a disturbance that travels through some material or substance called the medium for the wave.
• Note: The medium as a whole does not travel with the wave.
• Note: A wave transfers energy, but it does not transfer any material or substance outward from the source.
Waves carry energy because they can do work.
Water waves can move an object up and down or throw it on a beach.
Sound waves move your eardrum and you hear.
Light waves allow your eye to see and can make an image on film.
Most waves are caused by a vibration.
Particles in a medium can vibrate either up and down or back and forth.
Waves are classified by the direction that the particles in the medium move as a wave passes by.
Wave Phenomenon
• Wave phenomenon, energy can move from one location to another, yet the particles of matter in the medium return to their fixed position. A wave transports its energy without transporting matter.
Two types of Waves• Transverse waves
• Longitudinal wave
2. Longitudinal wave – particles vibrate parallel to the direction of the wave motion
Sound Waves
• A sound wave traveling through air is a classic example of a longitudinal wave.
1. Transverse waves – particles move perpendicular to the motion of the wave
Transverse waves
• Waves in the electromagnetic spectrum are Transverse Waves
Parts of a Transverse Wave
Crest CrestWavelength
Trough TroughWavelength
Amplitude
Normal
Parts of a Wave
• Crest - each high point of a wave
• Trough – each low point
• Wave length – distance between points where the wave pattern repeats itself
• Amplitude – any periodic motion, the maximum distance an object moves from equilibrium
Parts of a Longitudinal
Wave
Compressions
Rarefactions
Rarefactions• Rarefactions - are regions of low air
pressure
Compressions
Rarefactions
Compressions • Compressions are regions of high air
pressure
Compressions
Rarefactions
The difference between Transverse and Longitudinal
waves
• Transverse waves -are those in which displacement of particle is perpendicular to that of propagation of wave.
• Longitudinal waves - are those in which displacement of the particle is in a direction parallel to that of propagation.
Period – In a periodic motion, the amount of time required for an object to repeat one complete cycle
Periodic motion- wave move up and down at the same rate
PERIOD
Example: 1 wave every 20 seconds
Frequency – The number of wave crest that pass a point during one second.
( expressed in hertz)
Example: 3 waves per Second (3Hz)
Frequency Equation
• The frequency of a wave length is equal to the reciprocal of the period
• F=1/T
Hertz
• The symbol for frequency is f.
• The SI unit is hertz (Hz).
• One vibration/wave per second is 1 Hz.
• Two vibrations/wave per second is 2 Hz.
Wave length Equation
• The wavelength of a wave is equal to the velocity divided by the frequency
• Wavelength = V/f
Period & Frequency
Depends on?
The source
Does Not depend on?
The medium and wave’s speed
What affects the waves speed?
The speed of a wave depends on the medium in which the wave is traveling.
Light waves can move through air faster than they can move through water. This is why a pencil will look broken when it is placed in a glass of water. Exactly where does the pencil look broken?At the junction of the two different mediums.
Sound travels faster in water than in air. Sound travels faster in solids than in liquids. Why do you think this is so?
The closer the molecules are, the easier it will be for the molecules to bump into one another. This allows the vibrations to move faster, thus allowing the wave to move faster.
Comparing Light & Sound Waves • Light waves can move through air faster than
they can move through water. Because?....• Once the Light Wave enters another medium it
changes directions and slows down. • Sound travels faster in water than in air.
Because?....• The closer the molecules are, the easier it will be
for the molecules to bump into one another. This allows the vibrations to move faster, thus allowing the wave to move faster.
Doppler Effect
Doppler effect – a change in the frequency of a wave when the source or observer is moving
Reflection
• bouncing back of a wave when it meets a surface
Refraction
• the bending of waves as they pass from one medium into another
Diffraction
• bending of waves as they pass through narrow openings or around sharp corners
Interference
• Interference – the combination of two or more waves that exist in the same place at the same time
Interference Waves
• Interference of light is difficult to observe since the waves are so small and the vibrations so rapid.
• However, interference takes place with any kind of wave motion, and the effects of interference can be more easily seen by the examining the behavior of water waves, which are in many ways similar to light waves, but travel more slowly and are more easily noticeable.
Constructive interference
Constructive interference – waves combine to make a larger wave
Destructive interference
• Destructive interference – waves combine to make a smaller wave
Interference – the combination of two or more waves that exist in the same place at the same time
Constructive interference – waves combine to make a larger wave
Destructive interference – waves combine to make a smaller wave
Review
• Mechanical waves (sound, ocean waves, seismic) require a medium (air, water, ground) to travel through.
Electromagnetic Waves
Electromagnetic waves – waves that are caused by a disturbance in electric and magnetic fields and does not require a medium to travel through
Electromagnetic waves are produced by the vibration of charged particles
Electromagnetic Waves
Electromagnetic Waves
• Electromagnetic waves are created by the vibration of an electric charge.
• This vibration creates a wave which has both an electric and a magnetic component.
• An electromagnetic wave transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly represented by the symbol c).
Examples of electromagnetic waves:
Radio waves
Visible light waves
X-rays
Ultra-violet waves
Infrared waves
Microwaves
Lower energy
Longer wavelength
Higher energy
Shorter wavelength