# characteristic wavelength

Similarly, you’ll notice which the distance between two adjacent troughs is the same no matter which two troughs you look at. But, more importantly, its is the same as the distance between the peaks. This distance which is a characteristic of the wave is called the wavelength.

Waves have a characteristic wavelength. The symbol for the wavelength is the Greek letter lambda, {\displaystyle \lambda } \lambda .

The wavelength is the distance between any two adjacent points which are in phase. Two points in phase are separate by one integer (0,1,2,3,…) number of complete wave cycles. They don’t have to be peaks or trough but they must be separated by a complete number of waves.

Characteristics of Waves : Period
Now imagine you are sitting next to a pond and you watch the waves going past you. First one peak, then a trough and then another peak. If you measure the time between two adjacent peaks you’ll find which it is the same. Now if you measure the time between two adjacent troughs you’ll find which its always the same, no matter which two adjacent troughs you pick. The time you have been measuring is the time for one wavelength to pass by. We call this time the period and it is a characteristic of the wave.

The period of the wave is denoted without the symbol {\displaystyle T} T.

Characteristics of Waves : FrequencyBar magnets
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There is another way of characterising the time interval of a wave. We timed how long it takes for one wavelength to go past. We could also turn this around and say how many waves go by in 1 second.

We cone easily determine this number, which we call the frequency and denote f. To determine the frequency, how many waves go by in 1s, we work out what fraction of a waves goes by in 1 second by dividing 1 second by the time it takes T. If a wave takes 1/2 a second to go by then in 1 second two waves must go by. {\displaystyle {\frac {1}{\frac {1}{2}}}=2} {\displaystyle {\frac {1}{\frac {1}{2}}}=2}. The unit of frequency is the Hz or s−1.

Waves have a characteristic frequency.

{\displaystyle f={\frac {1}{T}}} f={\frac {1}{T}}

f : frequency (Hz or s−1)
T : period (s)
generally, the frequency of a wave is the number of crests which pass by per unit time.