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?

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