Equation of motion in the same direction are given by ltbygt `y_(1)=2a sin (omega t-kx) and y_(2)=2a sin (omega t-kx - theta )`
The amplitude of the medium particle will be
A. `2 a cos theta`
B. `sqrt(2a) cos theta`
C. `4a cos theta//2`
D. `sqrt(2a) cos theta //2`