At a distance r(r > a) rom 21. consider a large block of dielectric with unitorm polarizationp. a thin disc-shaped cavity is cut within this block the axis of t

at a distance r(r > a) rom 21. Consider a large block of dielectric with unitorm polarizationP. A thin disc-shaped cavity is cut within this block the axis of the cavity being parallel to P. Show that the electric feld within the cavity due to surjace charyes on, une cavty 1s given by P/co. What would be the corresponding valuerot 'electric field when a long needle-shaped cavity is cut with its axis parallel to P? ped |Ans. Zero.]