A plane wave y = a sin(ω(t-x/v)) undergoes a normal incidence in a plane boundary separating medium m₁ and m₂ and splits into a reflected and transmitted wave having speeds v₁ and v₂ then:

a) v₁ < v₂
b) v₁ = v₂
c) v₁ > v₂
d) Can't be determined