Mechanical waves

Wave velocity
v = λ / T
Find   It is known that:
      =   

Wave velocity
v = λ * ν
Find   It is known that:
      =   

Wave transition to another environment
λ1 / λ2 = v1 / v2
Find   It is known that:
      =   

Interference maximum and path difference
Δ_d = k λ
Find   It is known that:
      =   

Interference minimum and path difference
Δ_d = (2k+1) * λ / 2
Find   It is known that:
      =