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+ Perceiving Sound. + Before we start! A review of Light.

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Presentation on theme: "+ Perceiving Sound. + Before we start! A review of Light."— Presentation transcript:

1 + Perceiving Sound

2 + Before we start! A review of Light

3 + Light vs. Sound LightSound - Transverse waves-Longitudinal waves Electromagnetic waves - mechanical waves: require a medium to travel.

4 + What do you think is going to happen? Make a prediction. What will happen when air is removed from the bell jar? Don’t forget to explain why.

5 + Make Observations

6 + Why did this happen?

7 + Sound is… A mechanical wave. Longitudinal wave. Produced by the vibration of an object and transmitted to the object’s environment. Requires a medium.

8 + The speed of Sound It changes from one medium to another.

9 + Why is that? Using the particle model to justify your answer. Why does sound travel faster in solids than in gases?

10 + The Decibel (Db) The unit of measurement for the intensity of sound. High Intensity sound = High amplitude = More Decibels. Low Intensity sound = Low amplitude = Low Decibels.

11 +

12 + The Decibel Scale All decibel measurements are not completely accurate, they are related to our perception by the human ear. A sound measuring 0 Db is can barely be heard by the ear. We measure variations on the scale by a factor of 10.

13 + A Sample of a Decibel Scale Another one can be found on p. 103 of your textbook.

14 + Try some Questions P. 118 # 8- 10

15 + Pitch and Frequency Lower Pitch = lower frequency sound. High Pitch = Higher frequency sound.

16 + Infrasound and Ultrasounds Infrasounds = sounds under 20Hz Used by some animals to communicate. E.g. Elephants Ultrasounds = sounds above 20 000 Hz Used in medical imaging Used by some animals like bats (echolocation)

17 + Can we hear all frequencies?

18 + What happens when you age?

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