Q. 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 $-30^{\circ} \le \theta \le 30^{\circ}$ is :
Solution:
Pam difference
$d \sin \theta= n \lambda $
where d = seperation of slits
$\lambda$ = wave length
$n = no$. of maximas
$0.32 \times 10^{-3} \; \sin \; 30 = n \times 500 \times 10^{-9}$
$n = 320$
Hence total no. of maximas observed in angular range $-30^{\circ} \le \theta \le 30^{\circ}$ is maximas = $320 + 1 + 320 = 641$
