2. Sound is…Watch the video and take down 3 keypoints about soundO http://www.youtube.com/watch?v=MFLeG JclQiI&feature=related
3. Longitudinal Waves and guitarWatch the video and answer the questions:(1) How did the air layers get into vibration?(2)Did the air layers move with the sound wave?(3) How did the air particles move relative to thedirection of the sound wave? O http://www.physicsclassroom.com/mmedia/waves/gsl.cf m O http://illuminations.nctm.org/ActivityDetail.aspx?ID=37
4. Production and Propagation of SoundO Sound is produced by vibrating sources in a medium.O The source cause the air particles to vibrate and the sound wave will propagate outwards in the form of a longitudinal wave.O When air particles are pulled together, a region of compression is formed. When they are pushed apart, a region of rarefaction is formed.
5. Bell Jar experimentWhat does the video tell you about how sound travel? O http://www.youtube.com/watch?v=ce7AMJ dq0Gw
6. 15.1 Sound WavesO Compressions and rarefactions propagate faster in denser medium High Speed of sound Low Solid Liquid GasO Speed of sound in air is about 330 m/s in air, 1500 m/s in water, 5000 m/s in metal.Qn: Why does sound travel faster in solid than in gas?O Sound cannot travel in vacuum because there are no particles to transmit the vibration.
7. Pitch of SoundO Watch the video and answer the questions belowO (1) how does the pitch change when the frequency of the sound wave change?O (2) what is the maximum frequency you can detect? http://www.youtube.com/watch?v=4nUkNvl8mQwO Human audible frequency is between 20 Hz to 20 000 Hz (or 20 kHz)
8. Pitch and FrequencyO The higher the frequency of the sound wave, the higher the pitch of the sound.
9. Loudness and AmplitudeO The higher the amplitude of the sound wave, the louder the sound.
10. A BC D Which sound or sounds has/have (a) the same pitch as A? (b) the same loudness as A? (c) the same pitch as B?
11. EchoO Echo is caused by the reflection of sound from a hard and flat surface like a wall or cliff.O Why can’t you hear the echo when you clap your hands next to a high wall?
12. Application of echo
13. Use of Echo to determine distanceO A man stands at the end of a long wall and claps his hands. If he hears his echo after 2 seconds, what is the length of the hall? (Take the speed of sound in air to be 300 m/s)
14. Use of Echo to determine distanceO A ship transmits a pulse of sound into the water and the receiver receives the reflection of the sound by a shoal of fish after 0.15 seconds. If the speed of sound in water is 1200 m/s, how far is the shoal of fish from the ship?