If an electron vibrates up and down $9000$ times in $3$ seconds, it generates an electromagnetic wave

having a

A$)$ frequency of $6000$ Hz$.$ B$)$ frequency of $1000$ Hz$.$

C$)$ frequency of $2000$ Hz$.$ D$)$ wavelength of $100$ km$.$

$1)$ write down formula $(2$p$),2)$ plug$-$in values $(2$p$)$; state result with units $(1$p