If the kinetic energy of a free electron doubles,its de-Broglie wavelength changes by the factor

Find the de Broglie wavelength associated with a Helium $(He)$ atom in Helium gas at room temperature $(27^{\circ}C)$ and $1$ atmospheric pressure.

An electron and a photon each have a wavelength of $1.00 \; nm$. Find
$(a)$ their momenta,
$(b)$ the energy of the photon,and
$(c)$ the kinetic energy of the electron.

If the kinetic energy of a free electron doubles,its de-Broglie wavelength changes by the factor

An electron is accelerated from rest through a potential difference of $V$ volt. If the de Broglie wavelength of the electron is $1.227 \times 10^{-2} \, nm$,the potential difference is $......V$.

If ${\lambda _p}$ and ${\lambda _\alpha }$ are the de-Broglie wavelengths associated with protons and $\alpha$-particles of equal kinetic energies,then: