Calculate the velocity of an electron having a de Broglie wavelength of $58 \ nm$ and mass $9.1 \times 10^{-31} \ kg$. Given: $h = 6.63 \times 10^{-34} \ Js$.

$A$ $0.66 \ kg$ ball is moving with a speed of $100 \ m/s$. The associated wavelength will be $(h = 6.6 \times 10^{-34} \ J \ s)$.

Which of the following has the largest de Broglie wavelength (all have equal velocity)?

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 frequency of the de-Broglie wave of an electron in Bohr's first orbit of a hydrogen atom is . . . . . . . . . . $\times 10^{13} \ Hz$ (nearest integer).
[Given: $R_H$ (Rydberg constant) $= 2.18 \times 10^{-18} \ J$,$h$ (Planck's constant) $= 6.6 \times 10^{-34} \ J \cdot s$]

If the mass of particle $B$ is four times the mass of particle $A$ and the velocity of particle $A$ is eight times the velocity of particle $B$,then the ratio of the de Broglie wavelength of particle $A$ to particle $B$ will be .......