An electromaghetic radiation has an energy 14 . 4keV . To which...

Recall the formula of energy,

$E = \dfrac{hc}{λ} =14 . 4 \times1000 \times1 . 6$\times {10}^{- 19}$J ⇒ \dfrac{hc}{λ} = \dfrac{6 . 6 \times {10}^{- 34} \times 3 \times {10}^{8}}{λ} =14 . 4 \times1000 \times1 . 6$\times {10}^{- 19}$J ⇒ \lambda = \dfrac{6 . 6 \times {10}^{- 34} \times 3 \times {10}^{8}}{14 . 4 \times 1000 \times 1 . 6 \times {10}^{- 19}J} =0 . 859$\times {10}^{- 10}m ⇒ \lambda \approx1\overset{∘}{A} \left(\text{X-rays}\right)