Light can shows both a wave theory and a particle theory at the same time. Some time, light behaves like a wave. Light waves are also electromagnetic waves for the reason that they are made up of electric (

**E**) and magnetic (**H**) fields.
Wavelength and frequency are two most important characteristics of waves.

The sine wave is the fundamental waveform in nature. When calculating light waves, we refer to the sine wave. The time period (T) of the waveform is one full

**0**to**360**degree sweep (complete revolution). The relationship between frequency and the period is shown by the equation:**f = 1 / T**

**T = 1 / f**

**Wavelength:**The space between peaks of a wave is known as wavelength, measured in meters, When we calculate the light, wavelengths are in the order of nano-meters (1 x 10-9)

**Frequency:**The number of peaks that will travel from point to point in one second. The measuring unit of Frequency is cycles per second. After the 19th century the name given to this is Hertz (Hz) the name of the wave discoverer of radio - Heinrich Hertz. 1 Hz = 1 cycle per second.

We can find the speed of a wave by multiplying the two units together. Wave's speed is measured in (distance) per second:

**Wavelength x Frequency = Speed**

**The Speed of Light:**

The speed of light is a universal constant, about

**300,000 km/sec or 186,000 m/sec**in a vacuum. The accurate speed of light is: 299,792.458 km/s
It takes just about 8.3 min from the sun to reach the earth, which is 150,000,000 km, and the light travels at

**300,000 km/s, (150.000.000 / 300.000 / 60 = 8.3)**.
The SI units for frequency (

**¦**), wavelength (**l**) and speed of light (**c**), we with this equation we can show the relation between wavelength, frequency and speed of light.l = c / ¦ |
¦ = c / l |