I got the idea.
I am not displaying standing waves on an oscilloscope, a standing wave
is not a time-varying voltage.
The standing wave is a voltage which varies with the position along
the line.
One more doubt----- for 'peak' points of standing waves, SWR needle
moves to 'low' positive db gain values(towards right-max.needle
deflection). Similarly, for trough points of standing waves ,SWR
needle moves to peak positive db values(towards left).
Why this contradiction exists ?