The figure shows a double slit experimental set up for observing interference fringes due to different interference component colours of white light. What would be the predominant colour of the fringes observed at the point.
(i) O (the central point)
(ii) P, where, `S_2P - S_1P =(lambda_b)/2` ?
(here, `lambda_b` is the wavelength of the blue colour).