2. Transverse wave and longitudinal wave
Direction of
wave
propagation
Transverse wave, motion in which all points on
the wave oscillate along paths at right angles to
the direction of propagation of the wave.
Longitudinal wave, motion in which all points on
the wave oscillate along paths parallel to the
direction of propagation of the wave.
4. Displacement-time, Displacement-distance graphs
Displacement
Displacement
1. What is the difference between the two graphs?
2. Which of the two graphs relate to
a) the motion of the particles
b) the motion of the wave
3. Which of the following parameters are common
for the motion of the particles and wave?
a) amplitude
b) frequency
c) period
d) wavelength
e) velocity
5. Wave equation: V=f ( f=1/T)
The frequency of
the wave is 25 Hz.
Determine the
a) amplitude and
b) wavelength
c) velocity
d) period
of the wave.
6. Travelling wave equation
The displacement y of a particle in the medium is
given as a function of x and t by
y(x,t) = A sin(kx - ωt + φ) (move to the right)
y(x,t) = A sin(kx + ωt + φ) (move to the left)
k is the wave number, k = 2π/λ,
ω = 2π/T = 2πf is the angular frequency of the
wave
φ is called the phase constant
Angular wave number, k, is the
number of radians per unit distance.
m 2 rad ( 1 cycle)
1 m 2 rad
m
k = 2/
The phase constant φ is
determined by the initial
conditions of the motion.
If at t = 0 and x = 0
the displacement y is zero, then
φ = 0 or π.
If at t = 0 and x = 0
the displacement has its
maximum value, then φ = π/2.
phase
7. When = 0
Derive the second and third equation from the
first one.
8. Conceptual Question
1. Why do sound waves die out over long distances?
2. Why does sound travel fastest in solids?
3. When a guitar string is plucked, the guitar string
oscillates as a result of waves moving through the
string. The vibrations of the string cause the air
molecules to oscillate, forming sound waves.
a) Is the f of the sound wave equal to the f of the
string?
b) Is the wavelength of the sound wave always equal
to the wavelength of the waves on the string?
4. Consider a wave produced on a stretched spring by
holding one end and shaking it up and down. Does the
wavelength depend on the distance you move your
hand up and down?
1. Sound travels through
atmosphere and the air
particles absorb the sound
energy causing the sound to
die out.
2. Particles in solids are close
together and can transfer
energy faster.
3. Yes,
Only yes if the two speeds are
equal.
4. No. It only affects the
amplitude of the wave. The
wavelength will depend on
the frequency you move your
hand up and down, and the
speed of the wave through
the spring.
