Two coherent plane light waves of equal amplitude make a small angle $\alpha (\alpha \ll 1)$ with each other. They fall almost normally on a screen. If $\lambda$ is the wavelength of the light waves,the fringe width $\Delta x$ of the interference pattern of the two sets of waves on the screen is:

  • A
    $\frac{2\lambda}{\alpha}$
  • B
    $\frac{\lambda}{\alpha}$
  • C
    $\frac{\lambda}{2\alpha}$
  • D
    $\frac{\lambda}{\sqrt{\alpha}}$

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