What is a
wave?
Prior Knowledge
• Have you ever seen, felt or made a wave??
• Where can you find waves??
• Compare and contrast the waves below:
• Think about what happens when a SUP is in the
Intracoastal Waterway and a motor boat passes by?
• The boat creates waves that move past the object, causing the SUP to bob up and down.
• The waves continue to move forward, but the object remains in approximately the same place.
• WHY? The boat disturbs the flat surface and that disturbance moves outward along the ICW.
What is a WAVE?
• A wave is any disturbance that
transfers energy through matter or space.
• Once the wave has moved, the disturbance is gone.
The energy carried by ocean waves
can break rocks.
• Waves are created when a source creates a vibration.
• Vibration- any movement that follows the same path repeatedly.
•Waves are moving energy!
•The energy causes materials to
vibrate.
Waves only carry energy, not
matter!
How do waves travel?
•The matter through which a wave
travels is called a MEDIUM.
Examples of Mechanical Waves:
• sound
• water
• ropes
• earthquakes
• tsunami waves
Mechanical Waves need a medium to travel through.
Mechanical Waves can be either Transverse or Longitudinal
Examples of Electromagnetic Waves:
• x-rays
• radio waves
• infrared radiation
• microwaves
• visible light
Electromagnetic Waves do
NOT need a medium to travel
through.
Characteristics of Waves
Horizontal line is X-axis. This represents normal or resting position of the medium. (calm sea or a tight rope)
Vertical Line is Y-axis. This shows vibrational movement of wave
• Crest- High point of the wave
• Trough- Low point of the wave
Amplitude
• Amplitude = wave height
• As energy increases, particles of medium are moved greater distance from rest.
Amplitude
• Larger amplitude = more energy
Wavelength
• Wavelength = distance between 2 crests or
troughs
Wavelength
Human eyes can detect electromagnetic waves with a wavelength between 400 and 700 nanometers
1 nanometer = 1 of a meter!!!
1,000,000,000
Wavelength
Human eyes can detect electromagnetic waves with a wavelength between 400 and 700 nanometers
Wavelength
Human eyes can detect electromagnetic waves with a wavelength between 400 and 700 nanometers
Wavelength
• shorter wave length = more energy
Frequency (Hertz / Hz)
• Frequency = the number of waves that pass by a point each second
Frequency (Hertz / Hz)
• Higher frequency = more energy
• Have you ever noticed that you hear thunder several seconds after you see lightning?
• They are produced at the same time but you see lightning first because light travels faster than sound.
Wave Speed
• Wave Speed = speed at which waves travel through a medium
• Speed = frequency x wavelength
Speed of Waves
• The speed of a wave depends upon the medium through which it is traveling.
• One property that affects the speed of mechanical waves is the density.
• The more dense the medium, the slower the speed of a wave in that medium
– Substance that is more dense, has more particles than a less dense substance
– Molasses vs Water
Speed of Waves
• Another property of a medium that affects speed of waves is elasticity.
• Elasticity- ability of a medium to return quickly to its original shape after being disturbed.
• Wave moves faster in a more elastic medium-particles return to their rest position more quickly.
Label parts of the waves
Transverse Waves:
Waves in which the motion of the medium is at right angles to the direction of the wave
Ex: Light waves
http://www.youtube.com/watch?v=UHcse1jJAto&feature=player _detailpage#t=8
Transverse Wave
rest position
• Clap your hands together near your face.
• Do you hear the clap? Do you feel the air striking your face?
• When you clap your hands, you move particles of air away from resting place and crowd them together
• Compression-space where particles are crowded together.
• Rarefaction-space where there are fewer particles
Longitudinal Waves:
• Wave that consists of a series of compressions and rarefactions
• Particles of the medium move in the same direction in which wave moves
Ex: sound waves
http://www.youtube.com/watch?v=aguCWnbRETU&feature=player_
embedded
Carry en
ergy alon
g the wave
Longitudinal Wave
rarefaction
What
interactions can
waves undergo?
Reflection
• Reflection- happens when a wave bounces after hitting a barrier.
Reflection
• All waves can be reflected.
Refraction
• Waves do not bend unless an object gets in their way.
• Waves travel in straight lines.
• Waves speed in constant only for a particular medium
• As a wave enters a different medium, its speed changes
• Refraction-Bending of waves due to a change in speed.
Refraction
• Refraction – is the change in direction of a wave when it changes speed as it travels from one material(medium) to another.
Refraction occurs when a wave changes speed.
Light waves change direction when they slow down as they pass from air to water.
Diffraction
• The bending of waves around an edge of an obstacle is called diffraction.
• Result of a new series of waves being formed when the original wave strike an obstacle
Diffraction
Sound wavelengths are MUCH longer than light wavelengths (measured in nanometers).
This is why you can hear someone talking in another room with an open door, even though you can’t see them.
nosey
Interference
• Interference happens when waves overlap.
• When 2 or more waves arrive at the same place at the same time
Constructive: amplitude increases
Destructive: amplitude decreases
Interference
Resonance
• Resonance – vibration produced in one object that is caused by the vibration produced in another
properties
• _________
• _________
• _________
• _________ can undergo
• ________
• reflection
• ________
• interference
types
are always can be either
do _____need a __________ need a __________
examples examples
• x-rays
• radio waves
• infrared radiation
• microwaves
• visible light
• sound
• water
• ropes
• earthquakes
• tsunami waves
WAVES
**Finish filling in this chart**
properties
• amplitude
• wave length
• frequency
• wave speed can undergo
• refraction
• reflection
• diffraction
• interference
types
Electromagnetic Waves
Mechanical Waves
are always can be either
do NOT need a medium need a medium
Transvers e
Longitudinal
examples examples
• x-rays
• radio waves
• infrared radiation
• microwaves
• visible light
• sound
• water
• ropes
• earthquakes
• tsunami waves
WAVES
**CHECK YOUR ANSWERS**
