Diffraction: Practice Problem & Solution
A parallel beam of monochromatic light of wavelength $5000 \AA$ is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed in focal plane. The first minimum will be formed for the angle of diffraction equal to (1993)
Short Solution (Best for NEET):
To solve this problem, we apply the core principles of Diffraction. Understanding the underlying formula is key to arriving at the correct answer below:
For the first minimum in a single slit diffraction pattern, $a \sin\theta = \lambda$. Thus, $\sin\theta = \frac{\lambda}{a} = \frac{5000 \times 10^{-10}}{0.001 \times 10^{-3}} = \frac{5 \times 10^{-7}}{10^{-6}} = 0.5$. Therefore, $\theta = \sin^{-1}(0.5) = 30^\circ$.
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