When 40 kV is applied across an X-ray tube, X-rays are obtained with a maximum frequency of 9.7 10¹⁸ Hz . Determine the value of the Planck constant from these data.

Step-by-step solution

The maximum energy of an X-ray photon is equal to the kinetic energy of the incident electron. E_ max = eV Given V = 40 kV , the energy in electron-volts is: E_ max = 40 10^3 eV Using the relation E_ max = h _ max , the Planck constant h is given by: h = E_ max _ max Substituting the given values: h = 40 10^3 9.7 10¹⁸ eV s h 4.12 10⁻¹⁵ eV s