Question

t takes 7.21 ⋅ 10 − 19 J of energy to remove an electron from an iron atom. What is the maximum wavelength of light that can do this?

Answer 1

276 nm

Explanation:

The equation relating the energy (E) and the wavelength (λ) of a wave is

E = (hc)/λ Multiply both sides by λ

Eλ = hc Divide both sides by E

λ = (hc)/E

h = 6.626 × 10⁻³⁴ J·s

c = 2.998 × 10⁸ m·s⁻¹

E = 7.21 × 10⁻¹⁹ J Calculate the wavelength

λ = (6.626 × 10⁻³⁴ × 2.998 × 10⁸)/7.21 × 10⁻¹⁹

λ = 2.76 × 10⁻⁷ m = 276 × 10⁻⁹ m = 276 nm