When two coherent sources interact with each other, there will be production of alternate bright and dark fringes on the screen . Young's double-slit experiment domonstrates the idea of making two coherent sources. For better visibility, one has to choose proper amplitude for the sources. The phenomena is good enough to satisfy the conservation of energy principle. The pattern formed in YDSE is of uniform thickness and is nicely placed on a long distance screen.
The best combination of independent sources to produce sustained pattern among the following is
`Y_(1) = a sin omega t` `Y_(2) = a cos omega t`
`Y_(3) = a sin (omega t + (pi)/(4))` `Y_(4) = 2a sin (omega t + pi)`

Options

A. `Y_(1), Y_(2)` only
B. `Y_(2), Y_(3)` only
C. `Y_(3), Y_(4)` only
D. none of these

Answer

d

Explanation

Sources are independent. They connot form a coherent source since `phi` cannot be constant with time. So choices (a),(b) and (c ) are wrong, i.e., choice (d) is answer