A beam of light of \lambda = 600 nm from a distant 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 first dark fringes on either side of the central bright fringe is:

  • Option 1)

    1.2 cm

  • Option 2)

    1.2 mm

  • Option 3)

    2.4 cm

  • Option 4)

    2.4 mm

 

Answers (1)

For diffraction; 1st minima is found at \Theta = \frac{\lambda}{b}

\lambda = wavelength

b = slit\:width

or tan \Theta = \frac{\lambda}{b}= \frac{y}{D}

y = \frac{\lambda D}{b}

\therefore distance between maxima on both side is \Delta y= \frac{2\lambda D}{b}

\Delta y= \frac{2\times600\times10^{-9}\times2}{10^{-3}}

\Delta y= 2400\times10^{-6}m

\Delta y=2.4mm

 

 


Option 1)

1.2 cm

This option is incorrect.

Option 2)

1.2 mm

This option is incorrect.

Option 3)

2.4 cm

This option is incorrect.

Option 4)

2.4 mm

This option is correct.

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