Question

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) $2 a_{0}, 6 a_{0}$ and $\pi $ rad
(II) $3 a_{0}, 5 a_{0}$ and $\pi$ and
(III) $9 a_{0}, 7 a_{0}$, and $3 \pi $ rad
(IV) $2 a_{0}, 2 a_{0}$ and 0 .
The pair/s which has greatest intensity is/are:

• A. I
• B. II
• C. II, III
• D. I, IV

Answer 1

Answer: (D)

The resulting amplitude in the given four cases are $4 a_{0}, 2 a_{0}, 2 a_{0}$ and $4 a_{0}$. Thus in case I and IV intensity will be maximum and equal.