1000 Problems Solved

A solid sphere has a charge $$Q$$ distributed in its volume with a charge density $$d=kr^a$$ where $$k$$ and $$a$$ are constants and $$r$$ is distance from center. If electric field at $$r=\frac R2$$ is $$\frac 18$$ times stronger than that of at $$r=R$$, find $$a$$.

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