Question

Out of the given four waves (1), (2), (3) and (4),

y₁ = 20 sin (100 pt) ……(1)

y₂ = 20 sin (101 pt) ……(2)

y₃ = 20 cos (100 pt) ……(3)

y₄ = 20.1 sin (100 pt) ……(4)

emitted by four different sources S₁, S₂, S₃ and S₄ respectively, interference phenomenon would be observed in space under appropriate conditions when –

• A. Source S₁ emits wave (1) and S₄ emits wave (4)
• B. Source S₂ emits wave (2) and S₄ emits wave (4)
• C. Source S₁ emits wave (1) and S₃ emits wave (3)
• D. Interference phenomenon cannot be observed by the combination of any of the above waves

Answer 1

Answer: (C)

Source S₁ emits wave (1) and S₃ emits wave (3)

Answer 2

The phase difference between l₁ and l₂ is constant $\frac{\pi}{2}$, which doesn't depend on time hence the waves are coherent.