What will be the change in phase of wave dueto reflection from free support?

Explanation

When a tanker accelerates a pseudo force exerted on oil and hence its surface does not remain horizontal .
Consider a small element of mass dm . The forces on it are shown as in figure .
For equailibrium , the force parallel to the slope, `(dm)acostheta=(dm)gsintheta)`
where the pseudo force exerted opposite to the acceleration (dm)a
`thereforeacostheta=gsintheta`
`thereforetantheta=(a)/(g)`=slope