Two solid metal spheres A and B, each of radius 
, are situated in a vacuum. Their centres are separated by a distance of 
, as shown in the figure below.
Both spheres are positively charged. Point P lies on the line joining the centres of the two spheres, at a distance 
from the centre of sphere A. The variation with distance of the electric field strength 
at point P is shown in the graph below.
Use the graph above to determine the ratio
Explain your working.
.
