WAVE ENERGY WAKE UP PEOPLE….IT’S MONDAY….LET’S GET STARTED!!!

Waves

Wave- a traveling disturbance that carries energy from one place to another. Waves do not carry matter. Vibration –gives the wave its energy.

Shoulder Partner What gives the wave its energy? How does it begin at all?

Medium Medium – the matter or substance the wave moves through. Ex: water is the medium for ocean waves; air is the medium for sound waves. –Waves that need a medium are called mechanical waves. –Waves that do not are called electromagnetic. Ex. Light, x- rays, microwaves.

Ocean Waves

Face Partner If a tree falls in the woods and no one is there to hear it…does it make a sound?

Parts of the wave… The highest point of a wave is called the crest. The lowest point of a wave is called the trough. Amplitude – from rest to crest, or rest to trough. Wavelength – distance between two crests or between two troughs.

Diagram of a wave

Amplitude

Table Talk If you are surfing, which part of the wave should you ‘ride’?

Frequency Frequency – the number of complete wave/unit time. (how quickly/slowly a wave occurs). Measured in Hertz (Hz); named after Heinrich Hertz. 1 hertz = one wave/ second.

The Nature of Waves

Types of waves Transverse waves – the wave moves up and down at right angles. Longitudinal waves – the wave moves back and forth in a series of compressions and rarefactions. –Compression – when particles are crowded together. –Rarefaction – a space where there are few particles.

Transverse wave

Longitudinal Waves

Shoulder Partner Based on this information, is it possible for the cup and string phones to work? Why or why not?

Last type… Surface wave – both transverse and longitudinal at the surface between two mediums. –Example: ocean waves between both ocean water and air.

Measuring waves… Speed of wave = wavelength x frequency. –Ex: a wave with a frequency of 5 hertz and a wavelength of 2 m is a speed of 10 m/sec. The speed depends on the medium it is traveling through.

Wave Interactions Reflection – the bouncing back of a wave after it strikes a boundary that does not absorb all of its energy. –Ex: looking into a mirror The law of reflection states that the angle of incidence (I) is equal to the angle of reflection (R) {exactly the same; only reversed}

Reflection

Wave Interactions cont. Refraction – the bending of waves due to a change in speed. –Example: light as it enters water is bent. Diffraction – the bending of waves around the edge of an obstacle. –Example: water waves bending around a floating log.

Refraction and Diffraction

Still more… Interference – when two or more waves arrive at the same time. –A. Constructive – when they form one stronger wave together. –B. Destructive – when they form one weaker wave together.

Interference WHICH TYPE OF INTERFERENCE WOULD THIS BE???

Face Partner What are the four types of interactions that affect waves?

Standing waves Standing wave – is a wave that does not appear to be moving.

Let’s get to what you’re actually interested in…