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AP EAMCET · PHYSICS · Wave Optics

If a slit of width ' \(x\) ' was illuminated by red light having wavelength \(6500 Å\), the first minima was obtained at \(\theta=30^{\circ}\). Then the value of ' \(x\) ' is

  1. A \(1.4 \times 10^{-4} \mu \mathrm{~m}\)
  2. B \(1.2 \times 10^{-5} \mathrm{~m}\)
  3. C \(1.3 \mu \mathrm{~m}\)
  4. D \(1.2 \mu \mathrm{~m}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(1.3 \mu \mathrm{~m}\)

Step-by-step Solution

Detailed explanation

In diffraction, for first minima, \(\begin{aligned} & x \sin \theta=1 \times \lambda=6500 \times 10^{-10} \\ & \Rightarrow \quad x=\frac{6500 \times 10^{-10}}{\sin 30^{\circ}}=1.3 \mu \mathrm{~m} \end{aligned}\)
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