List of top Physics Questions on Electromagnetic waves asked in GUJCET

If wavelengths of visible rays, microwaves and X-rays are $\lambda_v$, $\lambda_m$ and $\lambda_x$ respectively. Then out of the following which relation is correct one?
A charged particle oscillates about its mean equilibrium position with a frequency of $8 \times 10^9$ Hz. What is the frequency of the electromagnetic waves produced by the oscillator?