Question

The wavelength corresponding to a beam of electrons whose kinetic energy is 100 eV is
($h=6.6\times {10}^{-34}$ Js, $1eV=1.6\times {10}^{-19}J$ J,$m_e=9.1\times {10}^{-31}$ kg)

• A. 4.8 $A^0$
• B. 3.6 $A^0$
• C. 1.2 $A^0$
• D. 2.4 $A^0$

Answer 1

Answer: (C)

1.2 $A^0$

$\frac{1}{2}m{v}^2=100eV$

$mv=\sqrt{2\times 9.1\times {10}^{-31}\times 100\times 1.6\times {10}^{-19}}$

$so\lambda =\frac{h}{mv}$

$=1.2A^{\circ }$

So, the answer is option (C).