Question

What is the energy of a proton possessing wavelength $0.4\stackrel{o}{A}$?

• A. 0.51 eV
• B. 1.51 eV
• C. 10.51 eV
• D. 100.51 eV

Answer 1

The correct option is A 0.51 eV

de Broglie wavelength for proton , $\lambda =\frac{h}{\sqrt{2mE}}$

or $E=\frac{h^2}{2m{\lambda }^2}=\frac{(6.62\times {10}^{-34}{)}^2}{2(1.67\times {10}^{-27})(0.4\times {10}^{-10}{)}^2}=8.2\times {10}^{-20}J=0.51eV$

where $1eV=1.6\times {10}^{-19}J$