# Waves.

## Presentation on theme: "Waves."— Presentation transcript:

Waves

What is a wave? A repeating disturbance or movement that transfers energy through matter or space Waves transfer energy not matter. Waves can only exist as they have energy to carry. The water waves to the right are carrying energy but are not moving.

What are mechanical waves?
They require a medium. A medium is a form of matter (a substance or material) through which the wave travels and it can be a solid, liquid or gas. They are not capable of transmitting its energy through a vacuum (empty space), such as light from the sun

What are mechanical waves?
They are produced when a source of energy causes a medium to vibrate. Vibration is a repeated back and forth or up and down motion There are two types of mechanical waves based on how the wave moves: Transverse Waves Longitudinal Waves

Transverse Waves The matter vibrates perpendicular (at right angles) to the direction of the wave Electromagnetic waves and light waves Animation courtesy of Dr. Dan Russell, Kettering University

Transverse Wave Properties
The crest is the highest point The trough is the lowest point The rest position is the horizontal line representing the rope (medium) before it was disturbed. The wavelength is the distance from one point on the wave to the next corresponding adjacent point, such as crest to crest or trough to tough

Longitudinal Wave The matter vibrates parallel (same) to the direction of the wave sound waves Animation courtesy of Dr. Dan Russell, Kettering University

Longitudinal Wave Properties
The area squeezed together is called compressions like the crests on a transverse wave In the picture, where the parts of the medium (coils of the Slinky) are closer together than normal The areas spread out are called rarefactions like the troughs on a transverse wave In the picture, where the parts of the medium are farther apart than normal

Sound Waves Sound is a longitudinal wave which travels through the air through a series of compressions and rarefactions. Sound travels through air, but travels through other materials as well.

What is echolocation?

What is sonar? Sonar is a system that uses the reflection of underwater sound waves to detect objects. This has been used to find sunken ships and schools of fish.

What are seismic waves? An energy wave which vibrates through the earth’s crust as the crust bends or breaks. Seismic waves exist as transverse (secondary waves), longitudinal (primary waves) and both types (surface) of waves. Some travel through the earth (P and S waves) and some travel across the earth’s surface (surface waves).

Animation courtesy of Dr. Dan Russell, Kettering University

Surface Waves A combination of longitudinal & transverse
Animation courtesy of Dr. Dan Russell, Kettering University

Amplitude The amplitude of a wave is directly related to the energy of a wave. The amplitude of a longitudinal wave is determined by the closeness of the compressions. The closer the compressions and the farther the rarefaction lines. The amplitude of a transverse wave is determined by the height of the crest or depth of the trough.

Wavelength and Frequency
Wavelength is the distance between two corresponding parts of a wave. Transverse wave: a measure of distance from crest to crest or trough to trough Longitudinal wave: a measure of the distance between one compression and rarefaction to the next Frequency is the number of waves that pass through a point in a certain amount of time. The unit for frequency is waves per second or Hertz (Hz). One Hz = One wave per second.

Wavelength and Frequency
Wavelength and frequency are inversely related. A decrease in the wavelength, means the more times the wave will pass through a point in one second (an increased frequency). The larger the wavelength (or increased wavelength), the fewer times it will pass through a point in one second (a decreased frequency).

Electromagnetic Waves
Wave which is capable of transmitting its energy through a vacuum (i.e., empty space) Produced by the vibration of electrons within atoms on the Sun's surface Travel through space until they reach Earth