Question 1
Which statement about ultrasound is correct?
A
It is produced by a rapidly vibrating source.
B
It is uncomfortable to human ears.
C
Its frequency must be greater than 300 kHz .
D
It travels the fastest in a vacuum.
Question 2
The diagram shows the air molecules in part of a sound wave at a particular moment in time.
Which statement is not correct?
A
Earlier, there was compression at X .
B
Later, there will be a rarefaction at X .
C
This part of the wave is travelling horizontally across the page.
D
This part of the wave is travelling towards the top of the page.
Question 3
A boy shouts and hears the echo from a tall building 2.2 s later.
The speed of sound in air is .
How far away from the boy is the building?
A
150 m
B
300 m
C
360 m
D
730 m
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