Q139 / 150 · MHT CET 2021 (23 Sep Shift 1) · Physics

A beam of light having wavelength $5400 Å$ from a distance source falls on a single slit $0.96 \mathrm{~mm}$ wide and the resultant diffraction pattern is observed on a screen $2 \mathrm{~m}$ away. What is the distance between the first dark fringe on either side of central bright fringe?

  • A
    4.8 mm
  • B
    1.2 mm
  • Correct answer
    C
    2.4 mm
  • D
    3.6 mm

Solution

$$ \lambda=5.4 \times 10^{-7} \mathrm{~m}, \mathrm{D}=2 \mathrm{~m} \text { and } \mathrm{a}=0.96 \times 10^{-3} \mathrm{~m} $$ Distance between the dark fringes on either side of the central bright fringe $=\frac{2 \lambda \mathrm{D}}{\mathrm{a}}=2.4 \mathrm{~mm}$

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

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