Find the

(a) maximum frequency, and


(b) minimum wavelength of X-rays produced by 30 kV electrons.

(a) X-ray produced by the electron therefore has maximum photon energy (Ex) equal to energy (E) of the electron.

E = eV …(1)


Where magnitude of charge of the electron ‘e’ = 1.6 × 10-19 C


Accelerating potential is V = 30 × 103 V 3


Putting in equation (1) we get,


E = 1.6 × 10-19 C × 30 × 103 J


Also, Ex = hν


Where, Ex = maximum energy of the X-ray


And h = plank’s constant = 6.63 × 10-34 J. sec


ν = max. frequency of X-ray


vmax = Emax/h



vmax= 7.24 × 1018 Hz


Max. frequency of X-ray is 7.24 × 1018 Hz


(b) Minimum wave length (λ) of X-ray is given by the following relation.


Ex = hν = hc/λ


λ = hc / Ex


c = speed of light = 3 × 108 m/s



λ = 0.041nm


Minimum wave length of X-ray is equal to 0.041nm


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