Physics - Wave Optics Question with Solution | TestHub

Width of central maximum is given by

$w=\frac{2f\lambda }{a} \dots \left(i\right)$

Where$f$is the focal length of the lens, a is the width of slit and$\lambda$is the wavelength of light used.

From Eq. (i), it is clear that fringe width

$w\propto \lambda$

So, when blue light is used in the experiment instead of red light, the fringes will become narrower.