3. Applications of Sound Echo is a reflection of sound. Echoes are used to find objects under water. This is called echolocation .

4. Applications of Echo 1 To find submarines from surface ships. 2 In fishing boats, to find large shoals of fish. 3 To measure the depth of the sea. 4 to locate a sunken shipwreck or cargo

5. 1 To find submarines from surface ships.

6. 2 In fishing boats, to find large shoals of fish. 3 To measure the depth of the sea. Refer to TB pg. 216

7. Nature of sound waves: 1 are longitudinal waves 2 need a medium to travel 3 can be reflected 4 travel faster in a denser medium than in the less dense medium. 5 travel at a speed of 330 m/s in air at 25  C

8. Pitch and Frequency The sounds produced by the mouse and the girl are high pitch sound.

9. Pitch In musical scales, doubling the frequency of a note produces a sound one octave higher than the original sound. Halving the frequency produces a sound one octave lower. In general, higher frequency sound gives rise to higher pitch note. Refer to TB pg. 220

10. Compare the frequencies of sound with same loudness: Lower pitch sound with lower frequency Higher pitch sound with higher frequency

11. Range of Audio Frequency 20 Hz to 20 kHz Frequency Pitch

14. Compare the loudness of sound with same frequency louder sound with greater amplitude softer sound with smaller amplitude Louder musical notes can be produced by hitting the instruments harder so as to produce vibrations of greater amplitude.

15. Loudness of sound  Loudness is related to the objective quantity amplitude ,  The larger the amplitude the louder the sound.

19. Noise and Music Noise is sound with irregular waveform. Musical note is sound with regular waveform. sound from piano sound from violin

20. Comparing sound waves and light waves Feature Sound waves Light waves transfer energy yes yes can travel through solids, liquids and gases but need a medium vacuum, gases, some solid and liquids, no medium needed speed 330 m/s in air 1500 m/s in water 5 000 m/s in steel 3 x 10 8 m/s in air 2.2 x 10 8 m/s in water 2 x 10 8 m/s in glass type of wave longitudinal transverse typical frequency typical wavelength 1 kHz 10 cm or 1 m 5 x 10 Hz 5000 nm = 5 x 10 -7 m part of the electromagnetic spectrum no yes

21. Qus 3

22. Qus 4

23. Ultrasound

24. Ultrasound