The wavelength of Kα line in copper is 1.5Å. The ionisation energy of K electron in copper is

Options

(a) 11.2×10⁻¹⁷ J
(b) 12.9×10⁻¹⁶ J
(c) 1.7×10⁻¹⁵ J
(d) 10×10⁻¹⁶ J

Correct Answer:

12.9×10⁻¹⁶ J

Explanation:

Required ionization energy, E = hc / λ

E = 6.6 × 10⁻³⁴ × 3 × 10⁸ / 1.5 × 10⁻¹°

= 12.9 × 10⁻¹⁶ J