Page 39 - Q & A STPM 2022 Physics

Chapter
21 Sound Waves

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21.1 Propagation of Sound Waves

Section A Multiple-choice Questions

Question 1
The figure below is the displacement-distance graph of a sound wave travelling
in air in the +x-direction. The points P, Q and R have the same displacement.
Displacement, y

P Q R
0
Distance, x

The instantaneous directions of motion of the air molecules at P, Q and R are
correctly shown in
P Q R
A
B
C

D

Answer: A
Sound wave is a longitudinal wave. Displacement, y
Vibration of the air molecules is parallel
to the direction of wave propagation. P Q R
The figure shows the y-x graphs at time
= 0, and at time = ∆t. 0 Distance, x Semester
The arrows at P, Q and R indicate
the directions of the instantaneous
velocities, P (–), Q (+) and R (–). 3

399

021 STPM Q&A Physics T3.indd 399 17/02/2022 10:24 AM