Diffraction: Practice Problem & Solution
A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm. The aperture is illuminated normally by a parallel beam of wavelength $5 \times 10^{-5}$ cm. The distance of the first dark band of the diffraction pattern from the center of the screen is: (2016 - II)
Solution Explained:
To solve this problem, we apply the core principles of Diffraction. Understanding the underlying formula is key to arriving at the correct answer below:
The distance of the first minimum from the center is $y = \frac{\lambda D}{a}$. Here, $D = f = 60 cm$. So, $y = \frac{5 \times 10^{-5} \times 60}{0.02} = \frac{300 \times 10^{-5}}{2 \times 10^{-2}} = 150 \times 10^{-3} cm = 0.15 cm$.
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