Waves

Characteristics of Waves

Frequency

The number of waves that pass a point along a medium is known as the wave’s frequency. It is represented by the symbol f and is expressed in hertz (Hz), a unit named after Heinrich Hertz, a German physicist who was the first to send and receive radio waves. One Hz is equivalent to one wave passing a point in a medium in one second. Kilohertz (kHz), megahertz (MHz), and gigahertz (GHz) are bigger units of frequencies.

Waves with greater frequency indicate that more energy has been carried or transferred. Period and frequency are reciprocal of each other, hence,

\[ T = \frac{1}{f}, \quad f = \frac{1}{T} \]

Velocity

Waves carry energy from one point to another without carrying the particles of their medium with them. How fast waves move and carry energy is determined by the wave’s velocity. It is represented by the symbol v. Remember that describing motion requires data on distance traveled and time during which the body moves. The distance traveled by the wave is represented by the wavelength (λ), while the time of travel is represented by the period (T). Therefore, the velocity of the wave is determined by the equation.

\[ \text{velocity} = \frac{\text{wavelength}}{\text{period}} \quad \text{or} \quad v = \frac{\lambda}{T} \]

Manipulating the equation, λ = vT and T = λ/v.

Since period is the reciprocal of frequency then,

\[ v = \lambda \cdot \frac{1}{f} \]

So, v = λf.

Deriving from the equation of wave velocity,

\[ \lambda = \frac{v}{f} \quad \text{and} \quad f = \frac{v}{\lambda} \]