What voltage should be applied to an electron microscope to produce electrons with a wavelength of $\lambda = 1.0 \ \mathring{A}$ (in $V$)?

If the potential difference used to accelerate electrons is increased four times,by what factor does the de-Broglie wavelength associated with the electrons change?

If the kinetic energy of a free electron is doubled,by what factor does its de Broglie wavelength change?

The de Broglie wavelength of an electron accelerated to a potential of $ 400 \,V $ is approximately (in $\,nm$)

Both an electron and a photon have the same de-Broglie wavelength of $1.2 \ \text{Å}$. The ratio of their energies is nearly

According to the de-Broglie hypothesis, the ratio of the wavelength of a photon and that of an electron having the same energy $E$ is $(m = \text{mass of electron}, c = \text{velocity of light})$