AP EAMCET202018 Sep 2020Morning ShiftPhysicsWave OpticsActual
(P Q ) represents a wavefront and (A O ) and (B P ), the corresponding two rays. Find the condition on (Q ) for constructive interference at (P ) between ray (B P ) and reflected ray (O P ).
Options
- A( = 3 2 d )
- B( = 4 d )
- C( - = d )
- D( - = 4 d )
Correct answer
B. ( = 4 d )
Step-by-step solution
According to figure, point (P ) and point (Q ) are at same phase. According to figure, In ( P O R ), ( aligned & = P R O P = d O P & O P= d (i) aligned ) In ( Q O P ), ( aligned & & (90^ -2 ) & = O Q O P & & 2 & = O Q O P & & O Q & =O P 2 (ii) aligned ) ( ) Path difference, ( aligned & =O P+O Q=O P+O P 2 & =O P(1+ 2 ) [ 1+ 2 =2 ^2 ] & = d 2 ^2 [from Eq. (i)] & =2 d aligned ) But path difference is ( 2 ). ( aligned & & 2 d & = 2 & & & = 4 d aligned )