Waves & Vibrations Physical Science
Waves are common! • Examples of waves: • Sound waves, visible light waves, radio waves, microwaves, water waves, sine waves, cosine waves, telephone cord waves, stadium waves, earthquake waves, waves on a string, and slinky waves Queen Elizabeth’s “wave”
Waves • Anything that moves side to side, back and forth, or front to back and transfers energy from one place to another. Most common: Sound waves Ocean waves Light waves
How Waves Travel • When waves travel through a solid, liquid, or gas, they are called Mechanical Waves. • Common examples are SOUND waves • The matter which the wave travels through is called a MEDIUM.
How Waves Travel • Waves that can travel through empty space are called Electromagnetic Waves. • Electromagnetic waves include all light waves, microwaves, xrays, and radio waves. • Electromagnetic waves do not require a medium. • (refer to reference chart)
Shapes of Waves • Waves can be described using two models: • Transverse Waves • Longitudinal (also called compression) Waves • These two labels describe the way in which the wave moves.
Types of Waves • Transverse Wave • Particle motion is perpendicular to direction of energy travel
Types of Waves • Transverse Wave • A stadium wave is an example of a transverse wave
Orientation Transverse Wave • Visible light is one type of transverse wave
Types of Waves • Longitudinal Waves • Particle motion is parallel to direction of energy travel
Types of Longitudinal Waves • Sound is one type of longitudinal wave
Types of Waves • Surface waves are actually combinations of transverse and longitudinal waves • Water waves are a common combination wave
Types of Waves • Earthquakes are also a result of both types of waves
Other terms to know… • Frequency • How many waves per second • Measured in Hertz (Hz)
Frequency & Wavelength • The higher the frequency, the lower the wavelength. This relationship is called Non linear, Inversely Proportional.
Check your understanding! • What transfers energy from one place to another? • What is matter called that a wave passes through? • What are the two waves a wave travels? • What are the two shapes of waves? • What is the relationship between frequency and wavelength?
Check your understanding! • What transfers energy from one place to another? • What is matter called that a wave passes through? • What are the two waves a wave travels? • What are the two shapes of waves? • What is the relationship between frequency and wavelength? wave medium Mechanical and electromagnetic Transverse and longitudinal Non linear, Inversely Proportional
Is light a wave or a stream of particles? • The debate has been going on for centuries! • Light exhibits both particle-like and wave-like behavior
There are unique behaviors of waves • Interference • Polarization • Diffraction • These behaviors are dependent on BARRIERS, or anything that interrupts the travel of the wave.
What happens when two waves meet? • When two waves meet in the same medium, the waves interfere. • There are two possibilities • Constructive Interference • Destructive Interference
Types of Interference • Constructive Interference • Crest meets crest OR trough meets trough • Results in increased AMPLITUDE
Types of Interference • Destructive Interference • Crest meets trough • Results in decreased AMPLITUDE
Standing Waves • Standing waves are a result of waves that reflect back upon themselves making a pattern of constructive and destructive interference.
Polarization • Polarization is caused when light is filtered based on the direction of movement of the wave.
Check your understanding! • What is anything that interrupts the pattern of a wave? • What is it called when light is passed through a vertical or horizontal filter? • What is it called when a wave passes through a narrow slit? • What happens during destructive interference?
Check your understanding! • What is anything that interrupts the pattern of a wave? • What is it called when light is passed through a vertical or horizontal filter? • What is it called when a wave passes through a narrow slit? • What happens during destructive interference? barrier polarization diffusion a crest meets a node and they cancel each other out
How do waves interact with barriers that they can not go around? • They can be REFLECTED • They can be ABSORBED • They can be TRANSMITTED through something called REFRACTION
B C D A The Law of Reflection
The Law of Reflection • Where is the incident wave? • Where is the reflected wave? • Where is the angle of incidence? • Where is the angle of reflection? • A • D • B • C
Diffuse vs. Regular • Observe the different surfaces:
Diffuse Reflection • Rough Surface
What about black and white? White reflects all colors Black absorbs all colors (turns energy into heat)
What is Refraction? • Refraction is when a wave changes from one medium to another. • It is caused by the need to change speed in different substances.
Total Internal Reflection Refraction Partial Reflection Total Internal Reflection!
Check for understanding! • What are the three things light can do when it encounters a barrier it can not go around? • What color is an object that absorbs all wavelengths of light? • When a wave of light goes from air to water, it is called __________. • When 100% of the light wave is reflected due to a critical angle of incidence, it is called __________________.