Phys102
Term: 122
Online HW-Ch016-Lec03
Q1:
Fully destructive interference between two sinusoidal waves of the same frequency and
amplitude occurs only if they:
A.
B.
C.
D.
E.
travel in opposite directions and are in phase
travel in opposite directions and are 180 degree out of phase
travel in the same direction and are 180o out of phase
travel in the same direction and are 90 degree out of phase
travel in the same direction and are in phase
Ans:
𝐂
Q2:
Two identical traveling waves of amplitude 10.0 cm, moving in the same direction,
are out of phase by л/4 rad. Find the amplitude of the resultant wave
Ans:
YR,m = 2ym cos(φ/2) = 2 × 10 cos(π/8) = 18.48 cm
Q3:
A stone is dropped into a still lake water to displace its molecules by
y(x, t) = 0.2 sin(πx-0.5πt). When should a second stone be dropped, after the first, at
the same place to produce destructive interference? Ignore the time it takes the stone
to reach water.
Ans:
The destructive interference will occur if the phase difference is Δφ = π
∆t ∆φ
=
T
2π
∆φ
∆φ
π
∆t =
=
=
= 2s
2π/T
ω
0.5π
KFUPM-Physics Department
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