In this post we shall understand the various terms associated with Sinusoidal or Sine Wave. In the previous lesson, we had understood about Polarisation of EM Waves.

### SPEED OF EM WAVE

Radio Waves propagate or travel from one place to another in a sinusoidal or sine wave form. we had seen that the electrical and magnetic components are perpendicular to each other. The frequency of radio waves would be the same as that of the the current which caused the wave. Speed of EM waves is equal to the speed of light which is constant in vacuum. In other mediums the speed of radio waves vary from one another. For example, the speed of EM waves is higher over water or sea surface than over land areas.

### CYCLE – FREQUENCY – WAVELENGTH

One cycle of a radio wave is one complete set of values in a sine waveform. That means commencing from the start or mean position to maximum value, thereafter to minimum value, and finally back to the mean or starting position. Amplitude of a wave is the maximum displacement from its mean position.

Frequency in hertz is the number of cycles of the wave in one second. Wave length in meters is the distance travelled by the wave in one cycle. Frequency and wavelengths are inversely proportional to each other. Therefore, as frequency increases its wavelength decreases and vice versa.

### FREQUENCY – TIME PERIOD

Time period is the time taken by the wave to complete one cycle which is expressed in micro seconds which is 10^{–6} seconds. Time period and frequency are inversely proportional to each other.

- [TIME PERIOD = 1/ FREQUENCY]
- [FREQUENCY = 1/ TIME PERIOD]

The unit for measurement of frequency is hertz. Frequency of one hertz means one cycle per second. Just like kilograms, one Kilohertz would be 1000 Hertz or 10^{3} hertz. Similarly one mega hertz equals 1000 Kilohertz or 10^{6} hertz

In this post, we have understood some of the terms associated with a Sine Waveform, let us learn about the relationship between the Speed, Wavelength And Frequency of EM wave in our next lesson.