# data[].attributes.body
1. When the source moves toward a stationary observer, the effective ______________ for the waves _______________. Thus, the observed frequency is _____________ than the emitted frequency. ​

2. When the source moves away from a stationary observer, the effective ______________ for the waves _______________. Thus, the observed frequency is _____________ than the emitted frequency.​

3. When the observer moves toward a stationary source, the effective ______________ for the waves _______________. Thus, the observed frequency is _____________ than the emitted frequency.

# data[].attributes.headline
What role do sound waves play in sonar systems used in echolocation?

# data[].attributes.subject
What role do sound waves play in sonar systems used in echolocation?

# data[].attributes.body
By the ends of this lesson, students will be able to

1.Predict the behaviour of the sound waves including diffraction and reflection

2.Discuss the relationship of intensity with power and distance

3.Calculate the intensity of a sound source or the distance between it and the observer

4.Investigate and explain the Doppler effect.

# data[].attributes.body
Why do you think you couldn't speak when holding our breath?Consider the role of air in producing sound and how it affects speaking.

# data[].attributes.body
Why do you think that the person around the corner would hear the sound of a drum and not the high pitched piccolo?

# data[].attributes.body
How changing the distance and power of sound source affects the intensity?

# data[].attributes.body
Two cars, X and Y, are driving towards each other on a highway. Car X is moving at a speed of 120 m/s, while Car Y is moving at a speed of 90 m/s. If the horn of car X emits a sound wave at a frequency of 600 Hz, what is the apparent frequency of the sound wave heard by a passenger in car Y? (Assume the velocity of sound in air is 340 m/s).

# data[].attributes.body
At a music festival, speakers at the main stage are 2 meters away from where Ali is standing and produce sound with an intensity of 5.0 x 10^-2 W/m^2. Ali moves away from the source of sound to a distance of 25m.Calculate the intensity of the sound reaching Ali?

# data[].attributes.body
Check your understanding