WHAT IS A WAVE?

INTRODUCTION Everything in the universe is one of two things, energy or matter.

INTRODUCTION Ever wonder how your television or your laptop or your cellphone or any other electrical device that you use every day works? It has to do with the movement of energy.

INTRODUCTION Next question, how does energy move? That has to do with waves.

INTRODUCTION Now I know that we have all seen waves in one form or another, be they waves that move across the top of a pond, or waves of heat that come up off the road during the middle of summer. Are those the kind of waves we are talking about?

INTRODUCTION The answer is yes, and no. Yes those are waves, yes they carry energy, no they don’t make your cell phone work. But they do share characteristics with the kind of waves that do make cell phones and appliances work.

INTRODUCTION Waves crashing on a beach show the tremendous energy waves can carry. A wave is a disturbance that transfers energy from place to place. In science, energy is defined as the ability to do work.

INTRODUCTION To understand waves, think of a boat on the ocean. If a wave disturbs the surface of the water, it will cause anything floating on the water to be disturbed too. The energy carried by a wave can lift even a large ship as it passes.

INTRODUCTION The disturbance caused by a wave is temporary. After the wave has passed, the water is calm again. What ever was floating on the surface will be returned to its original position.

INTRODUCTION In addition to learning about the different kinds of waves, we’ll learn the parts of these waves, how they move, their characteristics, and how they are alike and different from each other.

INTRODUCTION Did you see the ground as it moved after the blast? What you were seeing is a mechanical wave transferring energy through the earth. The earth, although it moved up and down, did not travel with the wave, only the energy was moving.

OBJECTIVE Identify a wave as energy traveling through a medium.

VOCABULARY Wave – disturbance that transfers energy from place to place. Mechanical wave – wave that transfers energy through matter. Electromagnetic wave – wave that transfers energy through empty space.

VOCABULARY Medium – material through which mechanical waves can travel. Solid, liquid, gas. Propagate – to generate or produce.

IN QUESTION Name at least 3 different types of waves that you have seen.

INTRODUCTION Let’s take a look at some general characteristics and types of waves.

WAVES NOTES All vibrations produce waves. All waves transfer energy through vibrations. All waves propagate from a source. (they spread out from the source)

INTRODUCTION There are two kinds of waves that we will learn about. Mechanical waves Electromagnetic waves

INTRODUCTION Now let’s take a look at mechanical waves.

NOTES Mechanical waves transfer energy through matter. Mechanical waves must have a medium to travel through, such as a solid, a liquid, or a gas.

NOTES There are two types of mechanical waves. Longitudinal waves Transverse waves

NOTES Transverse waves. Move up and down. Examples of these waves would be water waves or S type (secondary) earthquake waves.

NOTES Longitudinal waves. Move side to side. Examples would be sound waves or P type (primary) earthquake waves.

INTRODUCTION Lastly, let’s check out electromagnetic waves.

NOTES Electromagnetic waves transfer energy through empty space. Electromagnetic waves are always transverse waves. Examples of electromagnetic waves would be light, x-rays, television signals, and gamma rays.

OUT QUESTION S waves move up and down, P waves move side to side. Which type of earthquake wave do you think is more destructive and why? S waveP Wave