Presentation on theme: "Waves Objective: I will understand the difference between mechanical waves and electromagnetic waves."— Presentation transcript:
1WavesObjective: I will understand the difference between mechanical waves and electromagnetic waves.
2What is a wave?A wave is a moving disturbance that transfers energy through matter or space.
3What causes waves?Waves are created when a source of energy causes a medium to vibrate.A vibration is a repeated back and forth or up and down motion.
4Examples of wavesWater waves light waves Sound waves microwaves
5Radio waves X ray waves Ultraviolet waves seismic waves
6All of these waves can be put into 2 categories: Waves that do not require a medium2. Waves that require a medium
7So 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?
8Well, where does light come from? If it can travel through NOTHINGNESS, then it doesn’t need a medium
9How do mediums affect movement? Waves move through different mediums at different rates:Solid: a wave moves through a solid medium the fastestLiquid: a wave moves through a liquid medium slower than a solid, but faster than a gasGas: a wave moves through a gas medium the slowest
10MediumsThe medium can affect the speed of the wave travelling through it:An increase in the temperature of a medium increases the speed.An increase in the density of a medium increases the speed.
11Why do waves move through different mediums at different rates? Particles in a solid are closer together so they can move to each other quicker.Particles in a gas are farther apart so the energy takes longer to move from particle to particle.
12MediumsAs a wave moves the particles of matter do not move, only the energy is transferred.
13Back to our 2 groupsElectromagnetic 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 raysMechanical Waves are waves that require a medium in order to transfer energy.Ex. Sound waves, water waves, seismic waves
14Review What is a medium? Do electromagnetic waves require a medium? Give an example of an electromagnetic wave.In which medium do waves move the fastest?Do mechanical waves require a medium?Give an example of a mechanical wave.
19Let’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?
20WavesTypes of waves: Waves are classified according to how they move.
21Longitudinal Waves (Compressional 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 Examples: slinky, sound
22Longitudinal waves (where particles move parallel to the direction of the wave) are something you experience every day in the form of SOUND!
24Longitudinal/Compressional Wave Parts of a Longitudinal/Compression wave:Compression – space in a medium in which molecules are close together.Rarefaction- space in a medium where there are fewer or less molecules. The molecules are more spread out.Think of a slinky!!!
29ReviewIn a ___________ wave the particles of the medium vibrate PERPENDICULAR to the direction the wave is travelling.In a ___________ wave the particles of the medium vibrate Parallel to the direction the wave is travelling.Sound is an example of a ________ wave.Light is an example of a ________ wave.
31Objective: I will be able to identify the main parts of a wave. Wave PartsObjective: I will be able to identify the main parts of a wave.
32Basic Properties of Waves AmplitudeWavelengthFrequencySpeed
33WavelengthA wave travels a certain distance before it starts to repeat. The distance between two corresponding parts of a wave is its wavelength.Transverse measure from crest to crest or trough to trough.Longitudinal measure from one compression to the next.
34WavelengthThe distance between one point on a wave and the exact same point on the next wave
36AmplitudeThe maximum extent of vibration or the distance from the resting position of the medium to the crest or trough.
37AmplitudeThe amplitude of a transverse wave is the maximum distance the medium moves up or down (vibrates) from its rest position.The farther the medium moves as it vibrates the larger the amplitude of the resulting waves. The greater the amplitude the greater the amount of energy
46Measuring WavesThe speed, wavelength, and frequency of a wave are related to each other by a mathematical formula.Speed = wavelength x frequencyFrequency = speed/wavelengthWavelength = speed/frequencyWaves in different mediums travel at different speeds. However, in a given medium and under the same conditions the speed of the wave is constant.
47Measuring WavesRead pages in the purple Physical Science Book and do the 3 practice problems in your notebook.
48Answers 1. 1.2 m X 4.5 Hz = 5.4m/s 2. 10m X 2.0 Hz = 20 m/s m/s / .20 m = 128 hertz
55InterferenceConstructive interference occurs whenever two waves combine to make a wave with a larger amplitude.Destructive interference when the amplitudes of two waves combine producing a smaller amplitude.
56ResonanceMost objects have a natural frequency of vibration. Resonance occurs when vibrations traveling through an object match the object’s natural frequency.An object that is vibrating at its natural frequency absorbs energy from the objects that vibrate at the same frequency. Occurs in music.