The de Broglie wavelength of an electron with kinetic energy of $2.5 \ eV$ is (in $m$):
$(1 \ eV = 1.6 \times 10^{-19} \ J, m_{e} = 9 \times 10^{-31} \ kg)$

The wavelengths of electron waves in two orbits are in the ratio $3: 5$. The ratio of the kinetic energy of the electrons will be:

$A$ stream of electrons from a heated filament was passed between two charged plates kept at a potential difference $V$ esu. If $e$ and $m$ are the charge and mass of an electron, respectively, then the value of $h/\lambda$ (where $\lambda$ is the wavelength associated with the electron wave) is given by:

$C_{60}$ emerging from a source at a speed $(v)$ has a de Broglie wavelength of $11.0 \ \mathring{A}$. The value of $v$ (in $m \ s^{-1}$) is closest to
[Planck's constant $h = 6.626 \times 10^{-34} \ J \ s$]

Calculate the wavelength of an electron moving with a velocity of $2.05 \times 10^{7} \,m s^{-1}$.

The wavelength of an electron is $10^3 \ nm$. What is its momentum (in $kg \ m \ s^{-1}$)? $(h = 6.625 \times 10^{-34} \ J \ s)$