Q107 / 150 · MHT CET 2021 (24 Sep Shift 2) · Physics

The path difference between two interfering light waves meeting at a point on the screen is $\left(\frac{57}{2}\right) \lambda$. The band obtained at that point is

  • A
    $29^{\text {th }}$ bright band
  • B
    $57^{\text {th }}$ dark band
  • C
    $57^{\text {th }}$ bright band
  • Correct answer
    D
    $29^{\text {th }}$ dark band

Solution

Path difference $=\frac{57}{2} \lambda=28.5 \lambda$ Since the path difference is not an integral multiple of $\lambda$, it is not a bright bond. Path difference for $n$th dark band is given by $\left(n-\frac{1}{2}\right) \lambda$ Hence $\mathrm{n}=29$.

Hence, the correct answer is option: 'D'.

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