2. Position Plots
Also called snapshot graphs
Fixed time t
plot displacement as a function of
position
Shows the displacement of every
section of the medium
Determine from it:
Amplitude: maximum displacement
Wavelength: shortest distance over which
a wave repeats
4. Hint
Wavelength can be read off position plot as
it is the distance between 2 adjacent
repeating points
May be easier to use crests or troughs
Wave number = 2π / λ = 2π / wavelength
6. Time Plot
Also called history graph
Fixed position
plot displacement as a function of time
Shows how the displacement of a given
point varies with t
Determine from it:
Amplitude: maximum displacement
Frequency: how many cycles pass
through this given point in 1 second
11. Hint
• General equation of sinusoidal wave:
2πf = 2π/T
T = 1/f
•Period can be read off a time plot as it is
the shortest time before a wave repeats
13. A Comprehensive Question
Suppose graph c is obtained at x = 0 m and
the wave in graph c has a wave speed of 1.0
m/s. Determine the amplitude, frequency,
angular frequency, wavelength, phase
constant of the wave and write a
displacement equation for the wave.
14. Solution
Amplitude can be read off time plot as it is
the maximum displacement: 1.5
Frequency = 1 / T = 1 / π
Angular frequency = 2π / T = 2π / π = 2
Wavelength:
Wave speed = wavelength x frequency
Wavelength = v / f = 1 / (1 / π) = π
15. Solution (Cont’d)
Above is the general equation for sinusoidal waves
Plug in known values to find phase constant:
D (x,t) = 1.5 sin (2x – 2t + φ)
D(0,0) = 1.5 sin (φ)
0 = 1.5 sin φ
sin φ = 0
φ = 0