What are Waves?

waves

An example of waves is when you're on a raft and motorboat zooms by. The motorboat's energy causes waves in the water that move you and the raft. You can see and feel the water waves when you're on a swimming raft. There are many kinds of waves that affect you every day. Sound is a wave. Sunlight is a different kind of wave. Light, sound, and water waves may seem very different, but they are all waves.

What causes waves?

Energy is always required to make a wave. Mechanical waves are produced when a source of energy causes a medium to vibrate. When a vibration moves through a medium, a wave occurs. Moving objects have energy. A moving object can transfer energy to a medium, producing waves. For example, you can make waves by dipping your finger in water. Your finger has energy because it's moving. When your finger touches the water, it transfers energy to the water and makes waves. In the same way, a motorboat slicing through calm water transfers energy to the water and makes waves.

longitudinal waves

If you stretch out a spring toy and push and pull one end, you can produce a longitudinal wave. The coils in the spring move back and forth parallel to the wave motion. As compressions and rarefactions travel along the spring toy, each coil moves forward and then back. The energy travels from one end of the spring to the other, creating a wave. After the wave passes, each coil returns to the position where it started. Sound is also a longitudinal wave. In air, sound waves cause air particles to move back and forth. In areas where the particles are pushed together, compressions form. In between the compressions, particles are spread out. These are rarefactions.

How do waves transfer energy?

Mechanical waves travel through a medium, but they don't carry the medium with them. An example of this is a duck on a pond. When a wave travels under the duck, the duck move up and down. But the duck doesn't travel with the wave. After the wave passes, the duck and the water return the where they started. The medium doesn't travel with the wave because the medium is made up of tiny particles. When a wave enters a medium, it transfers energy to the medium's particles. The particles bump into each other, passing the wave's energy along. To understand this, think about how food is passed at a table. You hand the food to to the next person, who passes it to the next person, and so on. The food is transferred, but the people don't move. the food is like the wave's energy, and the people are like particles in a medium.

What carries waves?

Most kinds of waves need something to travel through. Sound waves travel through air. Water waves travel along the surface of the water. A wave can even travel along a rope. Gases (such as air), liquids (such as water), and solids (such as rope) all act as mediums. Not all waves require a medium to travel through. Light from the sun can carry energy through empty space. Waves that can travel without a medium are called electromagnetic waves.

types of waves

Waves move through mediums in different ways. Mechanical waves are classified by how they move. There are two types of mechanical waves: transverse waves and longitudinal waves.

transverse waves

When you make a wave on a rope, the wave moves from one end of the rope to the other. But the rope itself moves up and down or from side to side, at right angles to the direction in which the wave travels. Transverse means "across." As a transverse wave moves, the particles of the medium move across, or at right angle to, the direction of the wave.

representing types of waves

You can use diagrams to represent transverse and longitudinal waves. Transverse waves like those on a rope are easy to draw. You can draw a transverse wave as shown in the picture. Think of the horizontal line as the position of the rope before it's disturbed. This position is called the rest position. As a wave passes, the rope moves above or below the rest position. To draw longitudinal waves, think of the compressions in the spring toy as being similar to the crests of a transverse wave. The rarefactions in the spring toy are like the troughs of a transverse wave. By treating compressions as crests and rarefactions as troughs, you can draw longitudinal waves in the same way as transverse waves.

wave

a disturbance that transfers energy from place to place

vibration

a repeated back-and-forth or up-and-down motion

longitudinal waves definition

move the medium parallel to the direction in which the waves travel

energy

the ability to do work

crest

the high part of a transverse wave

trough

the low part of a transverse wave

medium

the material through which a wave travels

compressions

the parts of a longitudinal wave where the coils are close together

rarefactions

the parts of a longitudinal wave where the coils are spread out, or rarified

transverse waves definition

waves that move the medium at right angles to the direction in which the waves travel

mechanical waves

waves that require a medium through which to travel through