Question

Electron has energy of $100eV$ what will be its wavelength

• A. $1.2\stackrel{o}{A}$
• B. $10\stackrel{o}{A}$
• C. $100\stackrel{o}{A}$
• D. $1\stackrel{o}{A}$

Answer 1

The correct option is A $1.2\stackrel{o}{A}$

Energy is $E=100eV=100\times 1.6\times {10}^{-19}joule=1.6\times {10}^{-17}Joule$

Now its momentum will be $p=\sqrt[2]{22mE}$

putting the$mass$ of electron as $m=9.1\times {10}^{-31}Kg$

we get $p=5.4\times {10}^{-24}Kgm/s$

The de-broglie wavelength will be given by $\lambda =\frac{h}{p}$

put the value of Plank's constant as $h=6.62\times {10}^{-34}Js$ and the value of $p$

we get $\lambda =1.22\times {10}^{-10}m=1.22A^o$