We know that fringe width (β) in Young's double-slit experiment is given by \(\beta=\frac{\lambda D}d\), where D is the distance between the slit and the screen, d is the separation of slits and λ be the wavelength of light used.
- When the screen is moved away, the D increases and fringe width increases, and better interference fringes are seen.
- If the source is replaced by another source of shorter wavelengths, then the fringe, width decreases, and interference bands are not seen directly.