Q143 / 200 · Manipal (MET) 2012 · Physics

A beam of light of wavelength 600 nm from a source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fring is

  • A
    2.4 cm
  • Correct answer
    B
    2.4 mm
  • C
    1.2 mm
  • D
    1.2 cm

Solution

The distance between the first dark (minima) fringes on either side of the central maximum is twice the fringe width of either maximum or minimum, i.e., $\begin{aligned} \beta=2 \frac{D \lambda}{d} & =\frac{2 \times 2 \times 600 \times 10^{-9}}{1 \times 10^{-3}} \\ & =2.4 \times 10^{-3}=2.4 \mathrm{~mm} \end{aligned}$

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

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