Saved Bookmarks
| 1. |
Sound of wavelength λ passes through a Quincke’s tube, which is adjusted to give a maximum intensity I0. Through what distance should the sliding tube be moved to give an intensity I0/2? (a) λ/2 (b) λ/3 (c) λ/4 (d) λ/8 |
|
Answer» Correct Answer is: (d) λ/8 Let a = amplitude due to each wave. I0 = k(2a)2 = 4ka2. Let ϕ = phase difference to obtain the intensity I0 /2. Amplitude = a' = √(a2 + a2 + 2a2 cos ϕ) =2acos (ϕ/2). ∴ I0 /2 = k[4a2cos2(ϕ/2)] = I0cos2 (ϕ/2). or (ϕ/2) = 1/√2 or ϕ/2 = π/4 or ϕ = π/2 = 2π/λ Δ, where Δ = path difference. ∴ Δ = λ/4 = 2x, where x = displacement of the sliding tube. ∴ x = λ/8. |
|