Harmonic Wave Equation Calculator

Evaluate a sinusoidal traveling wave at any position and time, then find wave speed, angular frequency, and wave number.

Traveling harmonic wave
This calculator uses y(x,t) = A sin(kx - omega t + phase) for a wave traveling in the positive x direction.

About the harmonic wave equation

A harmonic wave is a repeating disturbance whose displacement varies sinusoidally with position and time. The standard traveling-wave expression used here is y(x,t) = A sin(kx - omega t + phase). Amplitude A is the greatest displacement from equilibrium, x is position, t is elapsed time, k is angular wave number, omega is angular frequency, and phase sets the wave's starting point in its cycle. Frequency tells how many complete cycles pass a fixed point each second and is measured in hertz. Angular frequency equals two pi times frequency and is measured in radians per second. Wavelength is the distance between corresponding points on adjacent cycles. Wave number equals two pi divided by wavelength and describes phase change per meter. Their ratio gives wave speed, equivalently frequency multiplied by wavelength. The minus sign before the time term describes propagation in the positive x direction. Replacing it with a plus sign would describe a wave moving in the negative x direction under this convention. The phase is entered in degrees for convenience and converted internally to radians before evaluating the sine. Phase values outside the usual zero-to-360-degree interval are mathematically valid because a sinusoid repeats every full cycle. Units must be consistent. With amplitude and wavelength in meters, position in meters, frequency in hertz, and time in seconds, displacement is in meters and wave speed is in meters per second. Other consistent length units can be used, but amplitude, wavelength, and position should then share that length unit. The sine argument itself must be dimensionless because each spatial and temporal contribution represents an angle in radians. Harmonic wave models appear in acoustics, optics, vibrating strings, water-wave approximations, and electromagnetic theory. A single ideal sinusoid extends indefinitely and has constant amplitude, unlike a finite pulse or damped oscillation. Real waves may disperse, attenuate, reflect, interfere, or contain many frequencies. This calculator evaluates one one-dimensional ideal component, making it useful for homework checks and physical intuition while keeping the sign and phase convention explicit.

Harmonic wave examples

These values demonstrate spatial phase, initial phase, and propagation through time.

Wave parametersDisplacementInterpretation
A 2 m, f 1 Hz, wavelength 4 m, x 1 m, t 0 s, phase 0 degrees2 mPosition is one quarter wavelength, so the sine reaches its maximum.
A 3 m, f 2 Hz, wavelength 5 m, x 0 m, t 0 s, phase 30 degrees1.5 mInitial phase alone sets the starting displacement.
A 1 m, f 0.5 Hz, wavelength 2 m, x 0 m, t 0.5 s, phase 0 degrees-1 mAfter one quarter period, the negative time term reaches minus pi over two.

How to evaluate a harmonic wave

  1. Enter the wave amplitude, frequency, and wavelength.
  2. Enter the position and time at which to evaluate the displacement.
  3. Enter the initial phase angle in degrees.
  4. Select Calculate wave and review displacement and derived wave properties.

Harmonic wave equation FAQ

What does wave amplitude represent?

Amplitude is the maximum magnitude of displacement from equilibrium. Wave energy often increases with amplitude squared, although the exact relation depends on the medium.

How are frequency and angular frequency related?

Angular frequency equals ordinary frequency multiplied by two pi. It expresses the oscillation rate in radians per second rather than cycles per second.

What is the wave number?

Wave number is two pi divided by wavelength. It gives the spatial phase change in radians per unit distance.

Why is there a minus sign before time?

The expression kx minus omega t maintains constant phase while x increases with time. It therefore represents travel in the positive x direction.

Can the displacement be negative?

Yes, the sign indicates which side of equilibrium the medium occupies at that position and time. It does not mean the amplitude itself is negative.