Properties of Waves
- Draw the above diagram for explaining transverse waves.
- For the case of longitudinal waves, draw a similar diagram, only the crests will be rarefactions and troughs will be compressions in this case.
Students should understand these points regarding the graphs:
1. The direction of oscillation has been shown on an axis perpendicular to the direction of propagation. However, the graph does not mean that these directions are perpendicular in both these cases.
2. On the graph of transverse motion, the y-axis shows "the displacement of the medium particles" in the y direction, from their equilibrium position whereas on the graph of longitudinal motion, "the displacement of the medium particles" from their equilibrium position in the x direction itself is plotted on the y-axis.
Refer to the above image to define the terms amplitude(A), Wavelength(λ), time period(T), frequency(f), time period(T) and velocity (v), stressing on the bolded keywords. If Simple Harmonic Motion has been taught before, then some of these terms will be a review to the students.
Amplitude (A) : The maximum displacement of the oscillating medium particles from the original position. Explain the terms Crests, Troughs, Rarefactions and Compressions. The units are that of distance.
Phase of Oscillation : Two particles are said to be in the same phase of oscillation when they are equally displaced from the original position and are moving in the same direction. The units are that of angle.
Wavelength (λ): The distance (measured in the direction of propagation of wave) between points of two points in the same phase of oscillation. The units are that of distance. Commonly Å(1 Angstrom is 10-10 meters)
Frequency (f) : The number of complete oscillations in a second made by a particle about the equilibrium position. It is quoted in hertz(Hz).
Time Period (T) : The time required for one complete oscillation of a particle is the time period. It is the reciprocal of frequency.
Velocity of a Wave (v) : The speed with which wave travels in a medium.