Question
Find the,
  1. maximum frequency, and
  2. minimum wavelength of X-rays produced by 30 kV electrons.

Answer

Potential of the electrons, V = 30 kV = 3 × 104 V

Hence, energy of the electrons, E = 3 × 104 eV

Where,

e = Charge on an electron = 1.6 × 10-19 C

  1. Maximum frequency produced by the X-rays = v

The energy of the electrons is given by the relation:

E = hv

Where,

h = Planck's constant = 6.626 × 10-34 Js

$\therefore\ \text{v}=\frac{\text{E}}{\text{h}}$

$=\frac{1.6\times10^{-19}\times3\times10^4}{6.626\times10^{-34}}=7.24\times10^{18}\ \text{Hz}$

Hence, the maximum frequency of X-rays produced is 7.24 × 1018 Hz.

  1. The minimum wavelength produced by the X-rays is given as:

$\lambda=\frac{\text{c}}{\text{v}}$

$=\frac{3\times10^{8}}{7.24\times10^{18}}=4.14\times10^{-11}\ \text{m}=0.0414\ \text{nm}$

Hence, the minimum wavelength of X-rays produced is 0.0414 nm.

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