Module 5 : MODERN PHYSICS
Lecture 26 : Wave Nature of Particle - the de Broglie Hypothesis
  Example 18
Find the wavelength spread of a 1 nano-second pulse from a ruby laser with a wavelength of 630 nm.
  Solution :
Since $ \Delta E\Delta t = h$, and $ E=h\nu$, we have $ \Delta\nu\Delta t = 1$. Thus $ \Delta\nu = 1/\Delta t = 10^9$ Hz.
 
Using $ \nu = c/\lambda$, we get
 
$\displaystyle d\nu = -\frac{c}{\lambda^2}d\lambda $
  so that
 
$\displaystyle \Delta\lambda = \frac{\lambda^2}{c}\Delta\lambda= 1.32\times 10^{-12}\ {\rm m}$

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