Answer:
The magnitude of the electric field at distance r from the point charge q is 
Explanation:
Suppose, Find E(r), the magnitude of the electric field at distance r from the point charge q.
We know that,
The electric field is proportional to the point charge and inversely proportional to the square of the distance from the charge point .
In mathematically,

Where, q = charge point
R = distance from charge point
Hence, The magnitude of the electric field at distance r from the point charge q is 