Waves

1. Waves • 7th grade science

2. Introduction • Audience: This lesson is for students in 7th grade. • Objective: Students will be able to identify a wave, understand that a wave is produced by vibrations in matter and demonstrate how waves transfer energy when they interact with matter.

3. Sound • Where does sound come from? • Where do you hear sound in the world around you? Click the ?

4. Sound • Where does sound come from? • Where do you hear sound in the world around you? Click the ?

5. Sound • Where does sound come from? • Where do you hear sound in the world around you? Click the ?

6. Sound • Where does sound come from? • Where do you hear sound in the world around you?

7. How does sound travel? • We have an idea of where sound comes from, but how does it get from where it is to us so we can here it? • How does sound travel? ?

8. Waves! • Sound travels in waves. But what is a wave? • A wave is caused when vibrations, or movement, is caused in matter, or the stuff around us. For example, the speakers on a radio use energy to vibrate the air around it. These vibrations travel through the air in a wave and eventually reach your ear which is what allows you to hear. Let’s Explore

9. Sound Waves • Sound waves are caused when objects create vibrations. This energy vibrates the air around it creating a wave. • When you pluck a guitar string, the string vibrates and produces a wave. • If you look at a speaker when it is playing you will see it vibrate. This produces a sound wave the same way the guitar does

10. True or False, a guitar string and a speaker make a sound wave the same way? True False

11. CORRECT! • Both the guitar and speaker create sound waves by making vibrations in the air

12. Not quite right… • Both the guitar and the speaker make sound waves by making vibrations in the air

13. Sound Waves You Can See • Take a look at this video of a speaker creating sound waves in water. The water allows us to see the waves that are being created since we can’t see the air around us. (click on the link to play video) Look for the vibrations in the water when the speaker is on and watch them stop when the speaker stops playing http://www.youtube.com/watch?v=_diS1twUbcU

14. Parts of a Wave • Now that we know that sound travels in waves there must be different parts of a wave because we hear different sounds. • There are 3 things that make up a wave. They are wavelength, frequency and amplitude.

15. Wavelength Crest • The wavelength is how far apart the waves are. This can be measure from either crest to crest or trough to trough. This is equal to one wave length. • Crest – top of the wave Trough – bottom of the wave Crest Trough Trough

16. Which letter represents the wavelength of this wave? A C B A – green line B – blue line C – red line

17. CORRECT! • The wavelength is the distance between two crests or two troughs

18. Not quite, try again… Remember a wavelength is either from crest to crest or trough to trough A C B A – green line B – blue line C – red line

19. Frequency Frequency is the number of waves that travel past a point every second. Therefore shorter wavelengths means higher frequency and longer wavelengths means a lower frequency. The more waves the higher the frequency. (Click the speaker to listen) Fewer waves means a lower frequency. (Click the speaker to listen)

20. Which wave has a lower frequency? Red wave Blue wave

21. CORRECT! The red line is a lower frequency because it has larger wavelengths and therefore less waves per second.

22. Not quite… Remember the frequency is the number of waves per second. The lower the frequency, the fewer waves per second. These waves will be more spaced out. Go back to review the information

23. Amplitude • The third part of waves is called the Amplitude. The amplitude is how much energy a wave has. If it is a sound wave then a bigger amplitude will mean it’s a louder sound High amplitude Low amplitude

24. Which wave has a biggest amplitude? 1 2 3

25. Not quite… Remember, amplitude is based on how tall the waves are. The taller the waves the bigger the amplitude and more energy the wave has High amplitude Low amplitude Go back to review the information

26. CORRECT! The taller the wave the bigger the amplitude. The bigger the amplitude the more energy a wave has. High amplitude Low amplitude

27. Different types of waves • There are other waves besides sound waves. Waves also move through the water and waves known as seismicwaves cause the Earth to shake during and earthquake. -

28. Waves have energy Waves move through matter, they do not push matter along. For example, waves in the ocean are not carrying a lot of water with them but are simply moving through the water. Watch this video to learn more about waves in the ocean and see an example http://www.youtube.com/watch?v=6pVmAho2ew8&feature=youtu.be

29. Waves Interacting with Matter When waves interact with matter, the energy they are carrying is transferred to that object causing it to vibrate. With sound waves that allows us to hear and with seismic waves during earthquakes, that can make buildings fall down. Click to the next slide to see an example of how waves interact with buildings and can knock them down.

30. Examples Click the link below to see an example of how waves in earthquakes transfer energy http://www.youtube.com/watch?v=MRNxhIatSec&feature=youtu.be

31. Quiz Time • In the upcoming quiz you will be answer questions about the different parts of waves, different types of waves, how waves are made and how they interact with matter. If you aren’t sure about any of those, go back to that section and review the material Back to Back to Back to parts of waves Types of waves How waves are made Back to Interacting with matter Proceed to the quiz

32. How does sound travel? Sound moves through the air into our ears Sound particles enter our ears By loud noises By making vibrations in the air

33. Click button to try again Try Again Back to studying Beginning of quiz

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35. True or false: A speaker can create sound with out creating vibrations? True False

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38. Which of these is not a part of a wave? The wavelength The frequency The threshold The amplitude

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41. Frequency is… The size of the wavelength Number of waves per second The amount of energy a wave has None of the above

42. Review what we learned earlier. Click button to try again Try Again Back to studying Beginning of quiz

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44. Waves transfer ______ to matter it interacts with. Water Information Energy Earthquakes

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47. In this video, vibrations are being transferred from what to what? Water  Speaker Speaker  Water Ground  Water Seismic waves  Sound waves Click link to play video http://www.youtube.com/watch?v=_diS1twUbcU

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50. Which wave has a larger amplitude, green or red? Red Green