Practice question

**X-rays from tube** maximum frequency f_max = e V/h, minimum wavelength λ_min = h c/(e V), Duane-Hunt law, for 10 kV f_max=1.6×10⁻¹⁹×10⁴/6.63×10⁻³⁴=2.41×10¹⁸ Hz, λ_min= c/f_max=0.124 nm, for 35 kV λ_min=1240/(35000) eV·nm? Actually 35 keV photon λ=1240/35000=0.0354 nm, for 15 kV 0.0827 nm, for 25 kV 0.0496 nm, for 30 kV 0.0413 nm. Photon energy E = (h c/λ) = (1240/400) = 3.1 eV . Kₘₐₓ = e V₀ = 0.8 eV . Φ₀ = E - Kₘₐₓ = 3.1 - 0.8 = 2.3 eV . Applying E = h f = h c/λ, p = h/λ, K_max = h f - Φ, Φ = h