JEE Main 2014 · 19 Apr · Shift 1 · Physics Q25

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PhysicsSingle correct+4 / -1Question 25 of 90

In a Young's double slit experiment, the distance between the two identical slits is 6.1 times larger than the slit width. Then the number of intensity maxima observed within the central maximum of the single slit diffraction pattern is :

Answer and worked solution

Official answer: C

The central diffraction maximum spans $a\sin\theta<\lambda$ . Interference maxima occur at $d\sin\theta=m\lambda$ , so they lie inside when $|m|<\frac da=6.1$ , i.e. $m=\pm1,\dots,\pm6$ .

That is six maxima on each side, 12 besides the central fringe, which is the keyed answer. (Counting the central $m=0$ fringe as well gives 13.)

Topics:Interference and Young's double slit Diffraction

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JEE Main 2014 · 19 Apr · Shift 1, Physics question 25