**Wavelength** is denoted **λ** ,is the difference between any two identical points of a wave.

The **frequency **of a wave is the number of wavelengths of that wave that pass a fixed point in one unit of that time , it is denoated by the greel letter **ν(nu**).

The wavelength and frequency of a wave are related to each other.The product of wavelength and frequecy is the total length of the ave that has passed the point is 1s.This length of wave per second is the speed of wave .For light of speed c

**C = ** **ν λ**

** the **speed of light waves depends on the medium through which they are pssing.In a vaccum,the speed is 3.00 x 10^8 m/s and the speed in air is only slightly .less.

Lets,see an example problem:

obtaining wavelength of light from its frequency;

Whats is the wavelength of the yellow sodium emission,which has a frequency of 5.09 x 10^14 /s?

Solution:

**Step 1**: the frequency and wavelength are related to each other by the formula **C = ** **ν λ**.Rearrange this formula to give:

** ** **λ= C/ ν**

**Step 2**: in the formula c is the speed of light 3x 1o^8 m/s.substituing;

**λ** = 3.00 x 10^8 m/s/ 5.09x10^14/s = 5.89 x 10^-7 m or 589 nm