An electron of mass

Question:

An electron of mass $m$ and a photon have same energy E. The ratio of wavelength of electron to that of photon is: (c being the velocity of light)

  1. $\frac{1}{c}\left(\frac{2 m}{E}\right)^{1 / 2}$

  2. $\frac{1}{c}\left(\frac{E}{2 m}\right)^{1 / 2}$

  3. $\left(\frac{E}{2 m}\right)^{1 / 2}$

  4. c $(2 m E)^{1 / 2}$


Correct Option: , 2

Solution:

$\lambda_{1}=\frac{\mathrm{h}}{\sqrt{2 \mathrm{mE}}}$

$\lambda_{2}=\frac{\mathrm{hc}}{\mathrm{E}}$

$\frac{\lambda_{1}}{\lambda_{2}}=\frac{1}{\mathrm{c}}\left(\frac{\mathrm{E}}{2 \mathrm{~m}}\right)^{1 / 2}$

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