Properties of Waves:
The distance between two successive crests or troughs of a wave is called wave length. It is denoted by Greek letter lambda (λ).
Its S.I. unit is metre (m). but for convenience it is often measured in nanometers and angstrom.
1 nm = 10-9 m
1 Ao = 10-10 m
The number of waves passing through a point in unit time is called frequency of waves. It is denoted by Greek letter nu (ע). Its S.I. unit is s-1 or hertz (Hz).
ע = c / λ
The distance covered by radiations in unit time (usually one second) is called speed of radiations. It is denoted by letter “c”. Its S.I. unit is m/s.
Speed of radiations is usually constant and is 3 x 108 m/s or 186000 miles/s.
Wave number :
Reciprocal of wavelength is called wave number. Wave number is also defined as “Number of waves in unit length.”
Its S.I. unit is m-1.