A source emits electromagnetic waves of wavelength 3 m . One beam reaches the observer directly and other after reflection from a water surface, travelling 1.5 m extra distance and with intensity reduced to 1 / 4 as compared to intensity due to the direct beam alone. The resultant intensity will be

Step-by-step solution

We know that a phase change of occurs when the reflection takes place at the boundary of denser medium. This is equivalent to a path difference of / 2 . Total phase difference = - =0 Thus, the two waves superimpose in phase. aligned & Resultant amplitude = I + ( I 4 ) = 3 2 I & Resultant intensity = ( 3 2 I )^2= 9 4 I= 9 4 fold. aligned