Q112 / 150 · MHT CET 2026 (15 April Shift 1) · Physics

Light of wavelength $\lambda$ is incident on a single slit of width 'a' and the distance between slit and screen is D. In diffraction pattern, if slit width is equal to the width of the central maximum then D is equal to

  • Correct answer
    A
    $\dfrac{a^2}{2\lambda}$
  • B
    $\dfrac{a}{2\lambda}$
  • C
    $\dfrac{a^2}{\lambda}$
  • D
    $\dfrac{a}{\lambda}$

Solution

The linear width of the central maximum in a single slit diffraction pattern is given by $W = \dfrac{2\lambda D}{a}$.

Given that the width of the central maximum is equal to the slit width, we have $W = a$.

Equating the two expressions:

$\dfrac{2\lambda D}{a} = a$

$2\lambda D = a^2$

$D = \dfrac{a^2}{2\lambda}$

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

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