Question

Four light waves are represented by
(i) $y=a_1\sin \omega t$
(ii) $y=a_2\sin \left(\omega t+\epsilon \right)$
(iii) $y=a_1\sin 2\omega t$
(iv) $y=a_2\sin 2\left(\omega t+\epsilon \right)$.
Interference fringes may be observed due to superposition of
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)

Answer 1

(a) (i) and (ii)
(d) (iii) and (iv).

The waves are travelling with the same frequencies and varying by constant phase difference.