JEE MAIN - Physics (2019 - 9th January Evening Slot - No. 13)
In a Young's double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength $$\lambda $$ = 500 nm is incident on the slits. The total number of bright fringes that are observed in the angular range $$-$$ 30o$$ \le $$$$\theta $$$$ \le $$30o is :
640
320
321
641
Explanation
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We know, path difference,
d sin$$\theta $$ = n$$\lambda $$
here n = no of bright fringer in the angle
here given
d = 0.32 $$ \times $$ 10-3 m
$$\lambda $$ = 500 $$ \times $$ 10$$-$$9 m
$$ \therefore $$ 0.32 $$ \times $$ 10$$-$$3 sin30o = n $$ \times $$ 500 $$ \times $$ 10$$-$$9
$$ \Rightarrow $$ n = 320
Total number of maxima in the range
$$-$$ 30o $$\theta $$ $$ \le $$ 30o is = 320 $$ \times $$ 2 + 1 = 641
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