The diffraction of an electron beam indicates that:

If the total energy of an electron in a hydrogen atom in an excited state is $-3.4 \text{ eV}$,then the de-Broglie wavelength of the electron is

The de-Broglie's wavelength of an electron in the $4^{th}$ orbit is . . . . . . . . $\pi a_0$. ($a_0 =$ Bohr's radius)

Which one of the following explains light both as a stream of particles and as wave motion?

The velocities of two particles $A$ and $B$ are $0.05 \ ms^{-1}$ and $0.02 \ ms^{-1}$ respectively. The mass of $B$ is five times the mass of $A$. The ratio of their de-Broglie's wavelength is

The velocity of an electron is $1\%$ of the velocity of light. Calculate the de-Broglie wavelength of the electron.