Question

what is wave length​

Answer 1

http://www.softschools.com/formulas/physics/wavelength_formula/5/

λ = wavelength, the distance between wave crests (m)

v = wave velocity, the speed that waves are moving in a direction (m/s)

f = frequency, the wave crests that go through a point in a certain time (cycles/s or Hz)

Answer 2

The distance between two successive
Crests or troughs of a wave.
OR
The distance between two sound waves is called wavelength.