Module 5 : MODERN PHYSICS
Lecture 26 : Wave Nature of Particle - the de Broglie Hypothesis
  Example 17
A beam of electrons with a de Broglie wavelength of $ 10^{-5}$ m passes through a slit $ 10^{-4}$ m wide. Calculate the angular spread of the beam by diffraction.
  Solution :
Initial momentum of the electron is along the x-direction.
 
$\displaystyle p_x = \frac{h}{\lambda} = \frac{6.63\times 10^{-34}}{10^{-5}}=6.63\times 10^{-29}\ {\rm kg\ m/s}$
  Due to the uncertainty in the position of the electron along the slit direction (y-direction), there is a momentum spread along the y-direction, given by
 
  See the animation

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