2WARM UP!What do you think of when you hear the word wave? Write a brief description of what you think a wave is. Then, write a short paragraph describing a time you might have experienced waves.
3START UP ACTIVITY TURN TO PAGE 573 COMPLETE THE ACTIVITY ON ENERGETIC WAVESON THE BACK OF YOUR WARM-UP ANSWER ANALYSIS QUESTIONS 1-3 IN COMPLETE SENTENCESTHIS WILL BE COLLECTED!
4REVIEW-What are the 7 forms of energy? 1. Mechanical (potential and kinetic)2. Electromagnetic (light)3. Chemical (stored in bonds-fuel, food, batteries)4. Electrical (movement of electrons)5. Thermal (heat)6. Nuclear (fission and fusion)7. Sound
5WHAT IS A WAVE? A TRANSFER OF ENERGY through matter OR empty space A MEDIUM is any material that a wave travels through. A medium can be a solid, liquid or gas.
6NATURE OF WAVESAs a wave travels, it does work on everything in its path.The waves in a pond do work on the water when it makes the water move up and down.The waves also do work on anything floating on the water’s surface.
7Can anyone describe the energy transfers that are occurring here? Moving ObjectWaves show transfer of energy from propeller through waterMedium=Water
8NATURE OF WAVESWaves travel through a medium, but they do not carry the medium with them.
17Time to PracticeUse your Slinky or rope to demonstrate a transverse wave:Work with a partnerOne of you move your end of the Slinky back and forth (left and right, like a snake crawling), perpendicular to its stretched length.The other student must hold his or her end of the Slinky stillA series of transverse waves will be generated and will travel through a medium (Slinky)
18LONGITUDINAL WAVESParticles move parallel to the direction of the waveWhen the particles move close together it is called COMPRESSION and when they move farther apart RAREFRACTION.
22LONGITUDINAL WAVESSound Waves are longitudinal waves. Sound waves travel by compressions and rarefactions of air particles.
23TIME TO PRACTICE! Use your Slinky to demonstrate a longitudinal wave: Work with a partnerStretch it out along the tableOne of you grasp and draw several coils of a stretched Slinky toward yourselfRelease the coilsThe other student must hold his or her end of the Slinky stillA longitudinal wave pulse will be generated and travel down the length of the Slinky.
24SURFACE/WATER WAVESSurface waves look like transverse waves, but the particles of the medium move in circles rather than up and down.
26What do you remember from last class? No notes allowed! Using a Venn diagram, compare and contrast mechanical and electromagnetic waves!Draw and label the parts of a transverse and longitudinal wave.Give one example of a type of energy that moves using a transverse wave, and one example of energy that moves using a longitudinal wave
27Let’s make a model! Fold your piece of paper in half hotdog style! 2) On the top half, use some yarn to make a transverse wave. Neatly label the crest and the trough!3) On the bottom half, make a longitudinal wave. Neatly label the compression and the rarefactionsNow…put it aside…we will add more later!
39WAVE SPEED! Speed, wavelength, and frequency are related! Different waves travel at different speeds.Speed = wavelength x frequency
40WARM UP: continued! Draw a transverse wave with a small amplitude! Draw a transverse wave with a large amplitudeHow can I measure amplitude in a longitudinal wave?Draw a transverse wave with a small wavelength.Draw a transverse wave with a large wavelength.How can I measure wavelength in a longitudinal wave?Draw a transverse wave with a high frequencyWhat 2 properties of wave affect wave speed?
41Questions we will answer today! How do waves interact with objects?How do waves behave when they move between different mediums (media)?How do waves interact with other waves?
42HOW DO WAVES INTERACT WITH OBJECTS? QUESTION 1HOW DO WAVES INTERACT WITH OBJECTS?
431. REFLECTIONWhen a wave hits an object through which it cannot pass, it bounces back. This is called REFLECTION.All waves can be reflected.
44ExamplesWhen light waves are reflected off an object, that means you can see that object. For example, light waves reflecting off the moon allow you to see the moon.When sound waves reflect it is called an echo!
45ReflectionWhen a wave reflects, the angle of incidence is equal to the angle of reflectionSee for yourself.
462. Absorption and 3. Transmission Waves that are not reflected are either absorbedORThey are transmitted (pass through the substance) like light through a glass window or a pair of glasses
474. DIFFRACTIONDiffraction is the bending of waves around a barrier or through a opening.The amount of diffraction of a wave depends on its wavelength and the size of the opening or barrier
48DIFFRACTIONIf the barrier or opening is larger than the wavelength of the wave, there is only small diffractionIf the barrier is smaller, the diffraction is larger
51LIGHT DIFFRACTIONA very simple demonstration of diffraction can be conducted by holding your hand in front of a light source and slowly closing two fingers while observing the light transmitted between them. As the fingers approach each other and come very close together, you begin to see a series of dark lines parallel to the fingers. The parallel lines are actually diffraction patterns. This phenomenon can also occur when light is "bent" around particles that are on the same order of magnitude as the wavelength of the light. A good example of this is the diffraction of sunlight by clouds that we often refer to as a silver lining, illustrated in Figure 1 with a beautiful sunset over the ocean.
53If you can hear it, why can’t you see it? The amount of diffraction depends on the wavelength and the size of the barrier.You can hear music around the corner of a building because sound has long wavelengths and are able to diffract around corners. You can’t see who or what is making the music because light waves are much shorter than sound waves so light is not diffracted as much.
54QUESTION 2HOW DO WAVES BEHAVE WHEN THEY MOVE BETWEEN MEDIUMS?
551. REFRACTIONREFRACTION is the bending of waves when waves move from one medium to another.When a wave hits a new medium, it changes speed and the wavelength changes!
57RAINBOWS ARE REFRACTED LIGHT When light waves from the sun pass through a droplet of water in the air, the light is refracted.The different colors of light travel at different speeds through the drop therefore the colors are refracted by different amounts= RAINBOW
59Question 3HOW DO WAVES INTERACT WITH EACH OTHER?
60INTERFERENCEYou already know that all matter has volume so 2 things cannot be in the same place at the same time.BUT WAVES ARE NOT MATTER…THEY ARE ENERGY SO 2 WAVES CAN BE IN THE SAME PLACE AT THE SAME TIME.
61INTERFERENCETWO WAVES CAN MEET, SHARE THE SAME SPACE AND PASS THROUGH EACH OTHER.WHEN 2 OR MORE WAVES OVERLAP, IT IS CALLED INTERFERENCE. THERE ARE TWO TYPES OF INTERFERENCE
62CONSTRUCTIVE INTEREFERENCE HAPPENS WHEN THE CRESTS OR TROUGHS OVERLAP TO COMBINE THEIR ENERGY TO MAKE HIGHER CRESTS OR DEEPER TROUGHS
63DESTRUCTIVE INTERFERENCE Destructive interference happens when the crest of one wave and the trough of another cancel each other.