Physics - Wave Optics Question with Solution | TestHub

The formula for fringe width is $W=\frac{\lambda D}{d}$ $\therefore \mathrm{W}\propto \lambda ,\mathrm{W}\propto \mathrm{D}$ and $\mathrm{W}\propto \frac{1}{\lambda }$ If the distance from the screen is increased, the width will increase. If the distance between the slit is decreased, the width will increase. As the wavelength will decrease the distance between the fringes will decrease. ${\lambda }_{\text{nd }}>{\lambda }_{\text{erex }}>{\lambda }_{\text{max }}$ $\therefore$ Blue light should be used.