Q. If yellow light emitted by sodium lamp in Young's double-slit experiment is replaced by a monochromatic blue light of the same intensity
NTA AbhyasNTA Abhyas 2022
Solution:
Fringe width is given by, $\beta =\frac{\lambda D}{d}$ , where $\lambda ,D\&d$ represents wavelength, screen distance and distance between the slits respectively.
So for same setup of Y.D.S.E., we can conclude from above formula that,
$\beta \propto \lambda ...\left(1\right)$
And we know from visible light spectrum, that $\lambda _{b l u e} < \lambda _{y e l l o w}$
So from $\left(1\right)$ , we can say
$\beta _{b l u e} < \beta _{y e l l o w}$
$\therefore $ Fringe width $\beta $ will decrease.
So for same setup of Y.D.S.E., we can conclude from above formula that,
$\beta \propto \lambda ...\left(1\right)$
And we know from visible light spectrum, that $\lambda _{b l u e} < \lambda _{y e l l o w}$
So from $\left(1\right)$ , we can say
$\beta _{b l u e} < \beta _{y e l l o w}$
$\therefore $ Fringe width $\beta $ will decrease.