Sodium and copper have work functions 2 3 ~ev and 4 5 ~ev respectively. The ratio of threshold wavelength of sodium to that of copper is nearest to

Step-by-step solution

The work function for a metal with threshold wavelength ₀ is given by = hc ₀ , where h is Planck's constant and c is the speed of light. Rearranging gives ₀ = hc for any metal. The ratio of threshold wavelengths for sodium and copper is therefore: _ 0, Na _ 0, Cu = _ Cu _ Na Given work functions _ Na = 2 3 = 6 eV and _ Cu = 4 5 = 20 eV , the ratio becomes: _ 0, Na _ 0, Cu = 20 6 = 10 3 3.33 Comparing with the options: A) 0.25 B) 4 C) 0.5 D) 2 The value 3.33 is nearest to option B. Final answer: B