Wave Optics

JEE Main level, numerical answer, medium

134 of 191

Question 134 of 191

A parallel beam of monochromatic light of wavelength 5000Ao5000A^{o} is incident normally on a single narrow slit of width 0.001mm0.001mm. The light is focused by convex lens on screen, placed on its focal plane. The first minima will be formed for the angle of diffraction of ______ (degree).

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Answer: 30

The condition for the first minima in the single slit diffraction experiment can be written as
asinθ=λ...(1)asin\theta =\lambda ...\left(1\right)
Equation (1) implies that
sin⁡θ=λa=5000×10−101×10−6=12\sin \theta =\dfrac{\lambda }{a} =\dfrac{5000\times {10}^{-10}}{1\times {10}^{-6}} =\dfrac{1}{2}
⇒θ=30∘\Rightarrow \theta =30^{\circ}

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