c)
se compun oscilatiile in paralel (vezi constructia Fresnel)
A²=A₁²+A₂²+2A₁A₂cosΔφ
A₁=1 cm;A₂=2 cm
Δφ=φ₂-φ₁=π/3-π/6=π/6
A²=A₁²+A₂²+2A₁A₂cosΔφ=1+4+4cosπ/6=5+2√3=8,46=>A=√8,46=2,9 cm
16.
φ₁=10π;φ₂=9π
Δφ=φ₁-φ₂=10π-9π=π=> se obtine un minim
A=A₁-A₂=4-3=1 mm (oscilatiile sunt in antifaza)
v=√(E/ρ)=√(2,7*10⁶/3000)=√9*10²=30 m/s
ω=600π rad/s
λ=2πv/ω=2π*30/600π=0,1 m=10 cm
