Waves Dude!

Surf’s up!

Waves transmit energy through Big Idea: Waves transmit energy through space and matter. Remember to take notes! Write was is in RED

The Nature of Waves What is a wave? A wave is a repeating disturbance or movement that transfers energy through matter or space.

Wave energy Most waves transfer energy by vibration of particles through a medium. Waves that require matter to transfer energy are mechanical waves. Remember the law of Conservation of Energy!! As the energy transfers from molecule to molecule, the energy moves farther and farther from the source of the disturbance.

Wave energy Sound is just energy moving air molecules. If there are no molecules, no sound is possible.

Waves A Wave is any disturbance that carries energy through matter or space.

Medium A medium is a substance through which a wave can travel. A medium can be a solid, liquid or gas. Waves that require a medium are called mechanical waves. i.e. water waves, sound, seismic.

Waves DO NOT carry the medium with them! They only move energy!! Think about passing food at the table. The food moves but the people don’t.

Waves use matter to transfer energy. The matter used to transport the wave is called a medium. A medium can be a gas, liquid, or solid.

Not all waves require a medium to travel. Light from the sun travels through empty space. Electromagnetic radiation does not need a medium.

Waves that do not require matter to transfer energy are electromagnetic waves. Electromagnetic waves can travel through a medium, but they can also travel in space or through a vacuum.

Radio waves, X-rays, microwaves, and visible light waves are examples of electromagnetic waves. They can all travel through empty space and they all travel at the same speed. This speed is sometimes called The Speed of Light. 186,000 miles per second!

Types of waves: Waves are classified according to how they move.

Slinky Wave Let’s use a slinky wave as an example. When the slinky is stretched from end to end and is held at rest, it assumes a natural position known as the equilibrium or rest position. To introduce a wave here we must first create a disturbance. We must move a particle away from its rest position.

Slinky Wave This disturbance would look something like this a LONGITUDINAL wave. The pulse is transferred through the medium of the slinky, but the slinky itself does not actually move. It just displaces from its rest position and then returns to it. So what really is being transferred?

Slinky Wave One way to do this is to jerk the slinky forward; the beginning of the slinky moves away from its equilibrium position and then back. The disturbance continues down the slinky. This disturbance that moves down the slinky is called a pulse. If we keep “pulsing” the slinky back and forth, we could get a repeating disturbance.

Longitudinal Wave The wave we see here is a longitudinal wave. The medium particles vibrate parallel to the motion of the pulse. (back and forth or, particles move in the same direction of the wave) This is the same type of wave that we use to transfer sound.

Compression The parts, where the coils are close together are called compressions, the parts where the coils are spread out are called rarefactions.

Click here to see compression waves in action! Mechanical waves in which medium matter moves forward and backward in the same direction the wave travels are longitudinal or compressional waves. Click here to see compression waves in action!

Transverse wave Waves that move the medium at right angles to the direction in which the waves are traveling are called transverse waves. This is an up and down movement. Transverse means “moving across”.

Example of transverse: Rope

Click here to see transverse waves in action! Mechanical waves in which matter moves up and down or back and forth at right angles compared to the direction of wave movement are transverse waves. Click here to see transverse waves in action!

In summary… Waves are classified into different types according to their natures : COPY THIS CHART

Combinations of waves Surface waves are a combination of transverse and longitudinal waves.The waves occur at the surface between water and air.

Combinations of waves Think raft in the ocean… A transverse wave can combine with a longitudinal wave to form a surface wave. The particles move in circles.

Anatomy of a Seismic Wave What are Seismic Waves? An energy wave which vibrates through the earth’s crust as the crust bends or breaks. Seismic waves are exist as both transverse and compressional waves. Some travel through the earth and some travel across the earth’s surface.

Properties of Waves

Draw a transverse wave on your paper.

Anatomy of a Wave In our wave here, the dashed line represents the equilibrium position (rest). Once the medium is disturbed, it moves away from this position and then returns to it

Anatomy of a Wave crest The points A and F are called the CRESTS of the wave. (Label Crest) This is the point where the wave exhibits the maximum amount of positive or upwards displacement

Anatomy of a Wave trough The points D and I are called the TROUGHS of the wave.(Label Trough) These are the points where the wave exhibits its maximum negative or downward displacement.

Basic Properties of Waves Amplitude Wavelength Frequency Speed

Anatomy of a Wave Amplitude The distance between the dashed line and point A is called the Amplitude of the wave. This is total energy carried.

Amplitude The larger the amplitude, the taller the wave is. 36

The amplitude of a transverse wave is determined by the height of the crest or depth of the trough

The amplitude of a compressional wave is how dense the medium is at each compression. Duh...…

Amplitude of a longitudinal wave. The amplitude of a longitudinal wave is a measure of how compressed or rarefied the medium becomes. Larger amplitude, more energy.

Anatomy of a Wave wavelength The distance between two consecutive similar points (in this case two crests) is called the wavelength. we will use the symbol  to represent wavelength Between what other points is can a wavelength be measured?

Wavelength cont. Longitudinal waves: measure from one compression to the next. The shorter the wavelength, the more the energy.

Anatomy of a Wave What else, about a wave, can we determine? Frequency and period and speed How could we find a frequency and speed of a wave?

Wave Speed Wave speed depends on properties of the medium Faster in liquids, than solids than gases. Why??? Light is slower in liquids and solids. Sound is faster in warm media.

Frequency - the number of complete vibrations (waves) per unit of time denoted by f and measured in units of Hz Period - the shortest time between each wave f = #/t

Frequency (ƒ) The number of complete waves that pass a given point in a certain amount of time. AKA number of vibrations per second. Frequency measured in hertz The higher the frequency, the more the energy.

Frequency 46

Draw Transverse wave and label: A, B, D, B-F, B-C If I only had a brain !