Practice question
Question
A photon of wavelength 250 nm strikes a metal surface. The ejected electron has a de Broglie wavelength of 1.0 × 10⁻⁹ m. What is the work function of the metal? (h = 6.626 × 10⁻³⁴ J s, c = 3.0 × 10⁸ m s⁻¹, mₑ = 9.1 × 10⁻³¹ kg)
Explanation
E = hc/λ ≈ 7.951×10⁻¹⁹ J. KE = h²/(2mλ²) ≈ 2.412×10⁻¹⁹ J. W₀ = E - KE ≈ 5.539×10⁻¹⁹ J.