STANDARD Physics Diffraction MCQ Question
A slit of width a is illuminated by white light. The first minimum for red light (λ = 6500 Å) will fall at θ = 30° when a will be
3200 Å
6.5 × 10⁻⁴ mm
1.3 micron
2.6 × 10⁻⁴ cm
Correct Answer
Detailed Explanation
For the first minimum, a sin θ = λ. Substituting the given values, a = λ/sin θ = 6500 × 10⁻⁷ / sin 30° = 1.3 micron.
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