Waves Objective I can describe the difference between

Waves Objective: I can describe the difference between mechanical waves and electromagnetic waves.

What is a wave? A wave is a moving disturbance that transfers energy through matter or space.

Examples of waves Water waves light waves Sound waves microwaves

Radio waves X-ray waves Ultraviolet waves seismic waves

All of these waves can be put into 2 categories: 1. Waves that do not require a medium 2. Waves that require a medium

So what’s a medium? A medium is something through which a wave travels. (solid, liquid, or gas!) • In a water wave, the medium is the water. • In a sound wave, the medium is the air. • In an earthquake, the medium is the ground. Does light require a medium?

Well, where does light come from? If it can travel through NOTHINGNESS, then it doesn’t need a medium

Back to our 2 groups 1. Electromagnetic waves can transfer energy through a medium OR through empty space (a vacuum) – Ex. Radio waves, light waves, infrared waves, ultraviolet waves, x-rays, gamma rays 2. Mechanical Waves are waves that require a medium in order to transfer energy. – Ex. Sound waves, water waves, seismic waves

Review 1. What is a medium? 2. Do electromagnetic waves require a medium? 3. Give an example of an electromagnetic wave. 4. Do mechanical waves require a medium? 5. Give an example of a mechanical wave.

Mechanical wave Electromagnetic wave

Transverse and Longitudinal Waves Objective: I will be able to differentiate between transverse and longitudinal waves.

2 different ways to create a wave:

Now lets see these two wave types in action http: //www. acs. psu. edu/drussell/demos/waves /wavemotion. html

Let’s look back at the waves Now, when you watch the waves, notice how the particles of the medium are moving in different ways. Note: • Which direction is the wave moving in? • Which direction are the particles moving in? • Are these two directions the same? http: //www. acs. psu. edu/drussell/demos/wavemotion. html

Longitudinal Waves In a longitudinal wave, the particles of the medium vibrate in the same direction as (or parallel to) the direction that the wave is travelling

Longitudinal waves (where particles move parallel to the direction of the wave) are something you experience every day in the form of SOUND!

Transverse Waves In a transverse wave, the particles of the medium vibrate in the opposite direction of (or perpendicular to) the direction that the wave is travelling

Transverse waves (where the particles move perpendicular to the direction of the wave) are also all around you in the form of LIGHT!

Review 1. In a ______ wave the particles of the medium vibrate PERPENDICULAR to the direction the wave is travelling. 2. In a ______ wave the particles of the medium vibrate PARALLEL to the direction the wave is travelling. 3. Sound is an example of a ____ wave. 4. Light is an example of a ____ wave.

Transverse Wave Longitudinal Wave

Wave Parts Objective: I will be able to identify and label the main parts of a wave.

Wavelength The distance between one point on a wave and the exact same point on the next wave

Amplitude The maximum extent of vibration or the distance from the resting position of the medium to the crest or trough

Frequency The number of waves produced in a given amount of time

Crest and trough The highest/lowest point of a transverse wave

Compression and rarefaction The squished up or spread out parts of a longitudinal wave

Review 1. Draw a transverse wave and label – – Wavelength Amplitude Crest Trough

Review, continued 2. Draw a longitudinal wave and label – Wavelength – Compression – rarefaction

Practice 1

Practice 2