WAVELENGTH OF WAVE IS DISTANCE MOVED DURING ONE OSCILLATION.
Distance between crest and next trough is half of the wavelength.
Therefore wavelength is λ = 2 × 10 cm= 20 cm .
FREQUENCY = ν = NUMBER OF RIPPLES PER SEC = 12/SEC = 12 HZ .
Velocity of wave = ν ×λ = 12/sec × 0·2m = 2·4 m/sec