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WAVES. WARM 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.

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Presentation on theme: "WAVES. WARM 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."— Presentation transcript:

1 WAVES

2 WARM 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.

3 START UP ACTIVITY TURN TO PAGE 573 TURN TO PAGE 573 COMPLETE THE ACTIVITY ON ENERGETIC WAVES COMPLETE THE ACTIVITY ON ENERGETIC WAVES ON THE BACK OF YOUR WARM-UP ANSWER ANALYSIS QUESTIONS 1-3 IN COMPLETE SENTENCES ON THE BACK OF YOUR WARM-UP ANSWER ANALYSIS QUESTIONS 1-3 IN COMPLETE SENTENCES THIS WILL BE COLLECTED! THIS WILL BE COLLECTED!

4 REVIEW-What are the 7 forms of energy? 1. Mechanical (potential and kinetic) 1. Mechanical (potential and kinetic) 2. Electromagnetic (light) 2. Electromagnetic (light) 3. Chemical (stored in bonds-fuel, food, batteries) 3. Chemical (stored in bonds-fuel, food, batteries) 4. Electrical (movement of electrons) 4. Electrical (movement of electrons) 5. Thermal (heat) 5. Thermal (heat) 6. Nuclear (fission and fusion) 6. Nuclear (fission and fusion) 7. Sound 7. Sound

5 WHAT IS A WAVE? A TRANSFER OF ENERGY through matter OR empty space 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. A MEDIUM is any material that a wave travels through. A medium can be a solid, liquid or gas.

6 NATURE OF WAVES As 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.

7 Can anyone describe the energy transfers that are occurring here? Moving Object Medium=Water Waves show transfer of energy from propeller through water

8 NATURE OF WAVES Waves travel through a medium, but they do not carry the medium with them. Waves travel through a medium, but they do not carry the medium with them.

9 Waves travel through a medium!

10 THERE ARE 2 MAJOR CATEGORIES OF WAVES MECHANICAL MECHANICAL ELECTROMAGNETIC ELECTROMAGNETIC

11 MECHANICAL WAVES Need a medium to transfer energy! CANNOT travel through empty space Need a medium to transfer energy! CANNOT travel through empty space OCEAN WAVES AND SOUND WAVES ARE EXAMPLES OCEAN WAVES AND SOUND WAVES ARE EXAMPLES

12 Electromagnetic Waves? Do not need a medium, CAN travel through empty space! Do not need a medium, CAN travel through empty space! Electromagnetic waves (light waves, microwaves, x-rays) can travel through empty space Electromagnetic waves (light waves, microwaves, x-rays) can travel through empty space

13 NATURE OF WAVES We now know that waves can be mechanical or electromagnetic, but there are also 3 types of waves: We now know that waves can be mechanical or electromagnetic, but there are also 3 types of waves: Three types of waves: Three types of waves:TRANSVERSELONGITUDINALSURFACE/WATER

14 TRANSVERSE WAVES Transverse waves move perpendicularly to the direction the wave is moving Transverse waves are made up of CRESTS and TROUGHS electromagnetic waves are examples of transverse waves.

15 TRANSVERSE WAVE!

16 /home/animations3/waves/wavemotion.ht ml /home/animations3/waves/wavemotion.ht ml /home/animations3/waves/wavemotion.ht ml /home/animations3/waves/wavemotion.ht ml

17 Time to Practice Use your Slinky or rope to demonstrate a transverse wave: Use your Slinky or rope to demonstrate a transverse wave: –Work with a partner –One 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 still –A series of transverse waves will be generated and will travel through a medium (Slinky)

18 LONGITUDINAL WAVES Particles move parallel to the direction of the wave Particles move parallel to the direction of the wave When the particles move close together it is called COMPRESSION and when they move farther apart RAREFRACTION. When the particles move close together it is called COMPRESSION and when they move farther apart RAREFRACTION.

19 LONGITGUDINAL WAVE vs. TRANSVERSE WAVES!

20 Vibrates parallel to (in the same direction of) wave travel Vibrates parallel to (in the same direction of) wave travel –sound waves –http://www.stmary.ws/highschool/physics/ho me/animations3/waves/wavemotion.html me/animations3/waves/wavemotion.htmlhttp://www.stmary.ws/highschool/physics/ho me/animations3/waves/wavemotion.html

21 LONGITUDINAL WAVES! /home/notes/waves/intro/video/Creating_ a_Longitudinal_Wave-1.mov /home/notes/waves/intro/video/Creating_ a_Longitudinal_Wave-1.mov /home/notes/waves/intro/video/Creating_ a_Longitudinal_Wave-1.mov /home/notes/waves/intro/video/Creating_ a_Longitudinal_Wave-1.mov

22 LONGITUDINAL WAVES Sound Waves are longitudinal waves. Sound waves travel by compressions and rarefactions of air particles.

23 TIME TO PRACTICE! Use your Slinky to demonstrate a longitudinal wave: Use your Slinky to demonstrate a longitudinal wave: –Work with a partner –Stretch it out along the table –One of you grasp and draw several coils of a stretched Slinky toward yourself –Release the coils –The other student must hold his or her end of the Slinky still –A longitudinal wave pulse will be generated and travel down the length of the Slinky.

24 SURFACE/WATER WAVES Surface waves look like transverse waves, but the particles of the medium move in circles rather than up and down.

25 A combination of longitudinal & transverse A combination of longitudinal & transverse

26 What do you remember from last class? No notes allowed! Using a Venn diagram, compare and contrast mechanical and electromagnetic waves! Using a Venn diagram, compare and contrast mechanical and electromagnetic waves! Draw and label the parts of a transverse and longitudinal wave. 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 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

27 Let’s make a model! 1) 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 rarefactions Now…put it aside…we will add more later!

28 PROPERTIES OF WAVES

29 THERE ARE 4 BASIC PROPERTIES OF WAVES! 1) AMPLITUDE 2) WAVELENGTH 3) FREQUENCY 4) SPEED

30 WHAT IS AMPLITUDE? AMPLITUDE IS THE GREATEST DISTANCE A WAVE MOVES AWAY FROM THE REST POSITION. AMPLITUDE IS THE GREATEST DISTANCE A WAVE MOVES AWAY FROM THE REST POSITION. LARGER AMPLITUDE = MORE ENERGY! LARGER AMPLITUDE = MORE ENERGY!

31 AMPLITUDE IN TRANSVERSE WAVES! Characteristics.html Characteristics.html Characteristics.html Characteristics.html

32 What about LONGITUDINAL WAVES? MEASURE OF HOW TIGHT THE COMPRESSIONS BECOME OR HOW LOOSE THE RAREFACTIONS. MEASURE OF HOW TIGHT THE COMPRESSIONS BECOME OR HOW LOOSE THE RAREFACTIONS.

33 WAVELENGTH The distance between any 2 corresponding points on a wave. The distance between any 2 corresponding points on a wave. For example, the distance between 2 crests in a transversal wave or 2 compressions in a longitudinal wave For example, the distance between 2 crests in a transversal wave or 2 compressions in a longitudinal wave

34 WAVELENGTH AND ENERGY SHORTER WAVELENGTH = MORE ENERGY SHORTER WAVELENGTH = MORE ENERGY HOW DOES SHAKING A ROPE OR A SLINKY AT DIFFERENT RATES AFFECT THE WAVELENGTH OF THE WAVE THAT MOVES THROUGH THE ROPE/SLINKY? HOW DOES SHAKING A ROPE OR A SLINKY AT DIFFERENT RATES AFFECT THE WAVELENGTH OF THE WAVE THAT MOVES THROUGH THE ROPE/SLINKY? WRITE A HYPOTHESIS? WRITE A HYPOTHESIS?

35 CHANGES IN WAVLENGTH! aves/introduction/introductionWaves.html aves/introduction/introductionWaves.html aves/introduction/introductionWaves.html aves/introduction/introductionWaves.html

36 How can you measure wavelength in longitudinal waves?

37 FREQUENCY The number of waves that pass a certain point in a given amount of time The number of waves that pass a certain point in a given amount of time Measured in HERTZ (HZ) Measured in HERTZ (HZ) If 1 wave passes in 1 second the frequency is 1 Hz! If 1 wave passes in 1 second the frequency is 1 Hz! HIGHER FREQUENCY = MORE ENERGY HIGHER FREQUENCY = MORE ENERGY /home/animations3/waves/Wave_Charact eristics.html /home/animations3/waves/Wave_Charact eristics.html /home/animations3/waves/Wave_Charact eristics.html /home/animations3/waves/Wave_Charact eristics.html

38 Let’s review! nce_share/vis_sim/wslm05_pg18_graph/w slm05_pg18_graph.html nce_share/vis_sim/wslm05_pg18_graph/w slm05_pg18_graph.html nce_share/vis_sim/wslm05_pg18_graph/w slm05_pg18_graph.html nce_share/vis_sim/wslm05_pg18_graph/w slm05_pg18_graph.html

39 WAVE SPEED! Speed, wavelength, and frequency are related! Speed, wavelength, and frequency are related! Different waves travel at different speeds. Different waves travel at different speeds. Speed = wavelength x frequency Speed = wavelength x frequency

40 WARM UP: continued! Draw a transverse wave with a small amplitude! Draw a transverse wave with a small amplitude! Draw a transverse wave with a large amplitude Draw a transverse wave with a large amplitude How can I measure amplitude in a longitudinal wave? How can I measure amplitude in a longitudinal wave? 4. Draw a transverse wave with a small wavelength. 5. Draw a transverse wave with a large wavelength. 6. How can I measure wavelength in a longitudinal wave? 7. Draw a transverse wave with a high frequency 8. What 2 properties of wave affect wave speed?

41 Questions we will answer today! 1) How do waves interact with objects? 2) How do waves behave when they move between different mediums (media)? 3) How do waves interact with other waves?

42 QUESTION 1 HOW DO WAVES INTERACT WITH OBJECTS? HOW DO WAVES INTERACT WITH OBJECTS?

43 1. REFLECTION When a wave hits an object through which it cannot pass, it bounces back. This is called REFLECTION. When a wave hits an object through which it cannot pass, it bounces back. This is called REFLECTION. All waves can be reflected. All waves can be reflected.

44 Examples When 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 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! When sound waves reflect it is called an echo!

45 Reflection When a wave reflects, the angle of incidence is equal to the angle of reflection When a wave reflects, the angle of incidence is equal to the angle of reflection See for yourself. See for yourself.

46 2. Absorption and 3. Transmission Waves that are not reflected are either absorbed Waves that are not reflected are either absorbedOR They are transmitted (pass through the substance) like light through a glass window or a pair of glasses They are transmitted (pass through the substance) like light through a glass window or a pair of glasses

47 4. DIFFRACTION Diffraction is the bending of waves around a barrier or through a opening. Diffraction 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 The amount of diffraction of a wave depends on its wavelength and the size of the opening or barrier

48 DIFFRACTION If the barrier or opening is larger than the wavelength of the wave, there is only small diffraction If the barrier or opening is larger than the wavelength of the wave, there is only small diffraction If the barrier is smaller, the diffraction is larger If the barrier is smaller, the diffraction is larger

49 WATER WAVE DIFFRACTION

50 DOUBLE SLIT DIFFRACTION

51 LIGHT DIFFRACTION A 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. A 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.

52 DIFFRACTION OF LIGHT THROUGH CLOUDS

53 If you can hear it, why can’t you see it? The amount of diffraction depends on the wavelength and the size of the barrier. 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. 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.

54 QUESTION 2 HOW DO WAVES BEHAVE WHEN THEY MOVE BETWEEN MEDIUMS? HOW DO WAVES BEHAVE WHEN THEY MOVE BETWEEN MEDIUMS?

55 1. REFRACTION REFRACTION is the bending of waves when waves move from one medium to another. REFRACTION 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! When a wave hits a new medium, it changes speed and the wavelength changes!

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57 RAINBOWS ARE REFRACTED LIGHT When light waves from the sun pass through a droplet of water in the air, the light is refracted. 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 The different colors of light travel at different speeds through the drop therefore the colors are refracted by different amounts= RAINBOW

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59 Question 3 HOW DO WAVES INTERACT WITH EACH OTHER? HOW DO WAVES INTERACT WITH EACH OTHER?

60 INTERFERENCE You already know that all matter has volume so 2 things cannot be in the same place at the same time. You 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. BUT WAVES ARE NOT MATTER…THEY ARE ENERGY SO 2 WAVES CAN BE IN THE SAME PLACE AT THE SAME TIME.

61 INTERFERENCE TWO WAVES CAN MEET, SHARE THE SAME SPACE AND PASS THROUGH EACH OTHER. TWO 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 WHEN 2 OR MORE WAVES OVERLAP, IT IS CALLED INTERFERENCE. THERE ARE TWO TYPES OF INTERFERENCE

62 CONSTRUCTIVE INTEREFERENCE HAPPENS WHEN THE CRESTS OR TROUGHS OVERLAP TO COMBINE THEIR ENERGY TO MAKE HIGHER CRESTS OR DEEPER TROUGHS HAPPENS WHEN THE CRESTS OR TROUGHS OVERLAP TO COMBINE THEIR ENERGY TO MAKE HIGHER CRESTS OR DEEPER TROUGHS

63 DESTRUCTIVE INTERFERENCE Destructive interference happens when the crest of one wave and the trough of another cancel each other. Destructive interference happens when the crest of one wave and the trough of another cancel each other.

64 VIDEO 6GFeI4 6GFeI4 6GFeI4 6GFeI4

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66 STANDING WAVES A wave that looks as though it is standing still, but it happens as a result of interference between waves and reflected waves. A wave that looks as though it is standing still, but it happens as a result of interference between waves and reflected waves. oqr70&feature=related oqr70&feature=related oqr70&feature=related oqr70&feature=related

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