Answer
(a) The frequency of the EM radiation is $1.5\times 10^{18}~Hz$
(b) This EM radiation lies in the X-ray part of the EM spectrum.
Work Step by Step
(a) We can find the frequency of the EM radiation:
$f = \frac{c}{\lambda}$
$f = \frac{3.0\times 10^8~m/s}{0.20\times 10^{-9}~m}$
$f = 1.5\times 10^{18}~Hz$
The frequency of the EM radiation is $1.5\times 10^{18}~Hz$
(b) Since a frequency of $10^{18}~Hz$ is in the middle of the range for X-rays, this EM radiation lies in the X-ray part of the EM spectrum.
