Physics - Wave Optics Question with Solution | TestHub

The interference patterns due to different component colours of white light overlap (incoherently). The central bright fringes for different colours are at same position. Therefore, the central fringe is white.

For a point P for which:

${\text{S}}_{\text{2}}{\text{P - S}}_{\text{1}}\text{P}={\lambda }_b/2$

${\lambda }_b\approx 4000 \stackrel{\circ }{\text{A}}$represents the wavelength of blue colour, the blue colour will be absent and the fringe will appear red in colour. Slightly farther away where,

${\text{S}}_{\text{2}}{\text{Q - S}}_{\text{1}}\text{Q}={\lambda }_b={\lambda }_r/2$

Where${\lambda }_r\approx 8000 \stackrel{\circ }{\text{A}}$represents the wavelength of red colour, the fringe will be predominantly blue.