A charge $+\mathrm{q}$ is placed somewhere inside the cavity of a thick conducting spherical shell of inner radius $\mathrm{R}_{1}$ and outer radius $\mathrm{R}_{2}$. A charge $-\mathrm{Q}$ is placed at a distance $\mathrm{r}>\mathrm{R}_{2}$ from the centre of the shell. Then the electric field in the hollow cavity-