Question

In a Young's double slit experiment, (slit distance $d$) monochromatic light of wavelength $\lambda$ is used and the fringe pattern observed at a distance $D$ from the slits. The angular position of the bright fringes are:

• A. $si{n}^{-1}\left(\frac{N\lambda }{d}\right)$
• B. $si{n}^{-1}\left(\frac{(N+\frac{1}{2})\lambda }{d}\right)$
• C. $si{n}^{-1}\left(\frac{N\lambda }{D}\right)$
• D. $si{n}^{-1}\left(\frac{(N+\frac{1}{2})\lambda }{D}\right)$

Answer 1

The correct option is A $si{n}^{-1}\left(\frac{N\lambda }{d}\right)$

Condition for bright friges :

Path difference, $\delta =dsin{\theta }_{bright}=N\lambda ,whereN=0,\pm 1,\pm 2,$

$\therefore {\theta }_{bright}=si{n}^{-1}\left(\frac{N\lambda }{d}\right)$