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# Harmonic waves

Physics 101 LO

Physics 101 LO

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### Harmonic waves

1. 1. HARMONIC WAVES IN WHALE SOUNDS
2. 2. WHALES PRODUCE SOUNDS FOR: Navigation Communication Hunting THE SPEED OF SOUND WAVES In air is ~340m/s In water is ~1500m/s
3. 3. HEARING RANGE Humans: 20 ~ 20,000 Hz Whales: 500 ~ 31,000 Hz
4. 4. QUESTION PART 1 Suppose that you and your friends were on a boat in the ocean. You were having a conversation when a whale swam by. The wavelength of the sound produced by you was approximately 17cm. Can the whale sense the sound?
5. 5. Hint 1: You are given the wavelength of the sound, can you find the frequency?
6. 6. Hint 1: You are given the wavelength of the sound, can you find the frequency? Hint 2: Use the equation: v=λf
7. 7. Solution:  v=λf  f= 𝑉 𝜆  = 340𝑚/𝑠 0.17𝑚  f=2000Hz  Note that frequency does not change when the wave moves from one medium to another  Whales can hear sound frequencies between 500 ~ 31,000 Hz ∴ The whale can sense the sound Rearrange the formula and solve for f Use the speed of sound in AIR because you and your friends are not underwater Watch out for units
8. 8. QUESTION PART 2 Whales use whistles for close- range communication. The whistles produced by the whale have a wave number of approximately 8π rad/m. Can you, standing on the boat, hear the whistles?
9. 9. Hint 1: You are given the wave number of the sound, can you find the wavelength?
10. 10. Hint 1: You are given the wave number of the sound, can you find the wavelength? Hint 2: Use the equation: k= 2𝜋 𝜆
11. 11. Hint 1: You are given the wave number of the sound, can you find the wavelength? Hint 2: Use the equation: k= 2𝜋 𝜆 Rearrange the equation and solve for λ λ= 2𝜋 𝑘 = 2𝜋 8𝜋 =0.25m
12. 12. Hint 1: You are given the wave number of the sound, can you find the wavelength? Hint 2: Use the equation: k= 2𝜋 𝜆 Rearrange the equation and solve for λ λ= 2𝜋 𝑘 = 2𝜋 8𝜋 =0.25m Find the frequency of the sound produced by the whale
13. 13. Solution:  k= 2𝜋 𝜆  λ= 2𝜋 𝑘 = 2𝜋 8𝜋 =0.25m  v=λf  f= 𝑉 𝜆 = 1500𝑚/𝑠 0.25𝑚  f=6000Hz  Note that frequency does not change when the wave moves from one medium to another  Humans can hear sound frequencies between 20 ~ 20,000 Hz ∴ You will be able to hear the whale whistle  Use the speed of sound in WATER because the whale is in water when it whistled
14. 14. Thank you for Watching
15. 15. WORK CITED  “Killer Whales Communication & Echolocation.” SeaWorld Parks & Entertainment. SeaWorld Parks & Entertainment. n.d. Web. 8 Feb. 2015. < http://seaworld.org/animal-info/animal- infobooks/killer-whale/communication-and-echolocation/>.  “Killer Whales Senses.” SeaWorld Parks & Entertainment. SeaWorld Parks & Entertainment. n.d. Web. 8 Feb. 2015. < http://seaworld.org/animal-info/animal-infobooks/killer- whale/communication-and-echolocation/>.