Force between two point electric charges kept at a distance of r in air is F. if these charges are kept at the same distance in water, how does the force between them change?

Force of attractio between two point electric charges placed at a distance .d. in a medium is F. What distance apart should these be kept in the same medium, so that between them beComes F//3

The force of attraction between two point charges placed at a distance 'd' apart in a medium is F. what should be the distance apart in the same medium so that the force of attraction between them becomes F/4 ?

Two point electric charges of value q and 2q are kept at a distance d apart from each other in air. A third charge Q is to be kept along the same line in such a way that the net force action on q and 2q is zero. Calculate the position of charge Q in terms of q and d.

The force acting between two point charges q_1 and q_2 kept at the same distance apart in air is attractive or repulsive when q_1q_2<0 .