The magnitude of the electrostatic force exerted on the particle by the electric field can be calculated using the formula F = qE, where F is the force, q is the charge of the particle, and E is the electric field strength.
Plugging in the given values, we get:
F = (3 x 10^-9 C) x (1500 N/C)
F = 4.5 x 10^-6 N
Therefore, the magnitude of the electrostatic force exerted on the particle by the electric field is 4.5 x 10^-6 N.