CIf the Assertion is correct but Reason is incorrect.
c
Cyclotron is used to accelerate charged partides. So Assertion is correct.
We know that time period of a particle
$\mathrm{T}=\frac{2 \pi \mathrm{r}}{\mathrm{v}_{0}} ; \frac{\mathrm{mv}_{0}^{2}}{\mathrm{r}}=\mathrm{Bqv}_{0} \Rightarrow \mathrm{v}_{0}=\frac{\mathrm{Bqr}}{\mathrm{m}}$
$\mathrm{T}=\frac{2 \pi \mathrm{r}}{\mathrm{Bqr}} \times \mathrm{m}=\frac{2 \pi}{\mathrm{Bq}} \mathrm{m}$
Frequency $=\frac{1}{\mathrm{T}}=\frac{\mathrm{Bq}}{2 \pi \mathrm{m}}$
This does not dpeend upon velocity so Reason is incorrect.