Two light waves arrives at a certain point on a screen. The waves have the same wavelength. At the arrival point, their amplitudes and phase differences are :
(I) `2a_(0),6a_(0)" and "pi " rad"` (II)`3a_(0),5a_(0)" and "pi " and"`
(III) 9a_(0), 7a_(0), " and "3pi " rad"` (IV) 2a_(0), 2a_(0) " and "0`.
The pair/s which has greatest intensity is/are :