Answer :

To find the frequency and energy of an X-ray with a given wavelength of [tex]\(2.090 \times 10^{-11} \)[/tex] meters, we can use the following formulae:

1. Calculating Frequency:
The relationship between the speed of light [tex]\(c\)[/tex], wavelength [tex]\(\lambda\)[/tex], and frequency [tex]\(f\)[/tex] is given by the formula:
[tex]\[ f = \frac{c}{\lambda} \][/tex]
Where:
- [tex]\( c \)[/tex] is the speed of light in a vacuum, approximately [tex]\( 3 \times 10^8 \)[/tex] meters per second.
- [tex]\( \lambda \)[/tex] is the wavelength of the X-ray, given as [tex]\( 2.090 \times 10^{-11} \)[/tex] meters.

Substituting the given values:
[tex]\[ f = \frac{3 \times 10^8}{2.090 \times 10^{-11}} \][/tex]

Performing the division:
[tex]\[ f \approx 1.435 \times 10^{19} \text{ Hz} \][/tex]

Therefore, the frequency of the X-ray is approximately [tex]\( 1.435 \times 10^{19} \)[/tex] Hertz.

2. Calculating Energy:
The energy [tex]\(E\)[/tex] of a photon is given by Planck's equation:
[tex]\[ E = h \cdot f \][/tex]
Where:
- [tex]\( h \)[/tex] is Planck's constant, approximately [tex]\( 6.62607015 \times 10^{-34} \)[/tex] Joule seconds (Js).
- [tex]\( f \)[/tex] is the frequency which we have calculated as [tex]\( 1.435 \times 10^{19} \)[/tex] Hz.

Substituting the values:
[tex]\[ E = 6.62607015 \times 10^{-34} \times 1.435 \times 10^{19} \][/tex]

Performing the multiplication:
[tex]\[ E \approx 9.511 \times 10^{-15} \text{ Joules} \][/tex]

Thus, the energy of the X-ray photon is approximately [tex]\( 9.511 \times 10^{-15} \)[/tex] Joules.

To summarize, for an X-ray with a wavelength of [tex]\( 2.090 \times 10^{-11} \)[/tex] meters:

- The frequency is approximately [tex]\( 1.435 \times 10^{19} \)[/tex] Hertz.
- The energy is approximately [tex]\( 9.511 \times 10^{-15} \)[/tex] Joules.