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In a single slit diffraction experiment, the width of the slit is increased. How will the (i) size and (ii) intensity of central bright band be affected? Justify your answer. - Physics

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Short Note

Answer the following question.
In a single slit diffraction experiment, the width of the slit is increased. How will the (i) size and (ii) intensity of central bright band be affected? Justify your answer.

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Solution 1

The size of the central maximum is given by `(2lambda)/a` where a is the slit width.
It is clear from the above expression if a is increased, the size of the central maximum will decrease.

However, the intensity changes because of two factors.
1. Increasing the width of the slit, causes more light energy to fall on the screen as compared to that with the original width.
2. The light energy is now squeezed into a smaller area on the screen because the size of the central maximum is reduced. The two factors make the intensity increase manyfold.

Solution 2

The size of the central maximum is given by `(2lambda)/a` where a is the slit width.
It is clear from the above expression if a is increased, the size of the central maximum will decrease.

However, the intensity changes because of two factors.

  1. Increasing the width of the slit, causes more light energy to fall on the screen as compared to that with the original width.
  2. The light energy is now squeezed into a smaller area on the screen because the size of the central maximum is reduced. The two factors make the intensity increase manyfold.
Concept: Diffraction - The Single Slit
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