The de-Broglie wavelength of a proton is twice the de-Broglie wavelength of an alpha particle. The ratio of the kinetic energies of the proton and the alpha particle is

If the de-Broglie wavelength of a neutron at a temperature of $77^{\circ} \mathrm{C}$ is $\lambda$, then the de-Broglie wavelength of the neutron at a temperature of $1127^{\circ} \mathrm{C}$ is

If Planck's constant is $6.63 \times 10^{-34} \mathrm{Js}$, then the slope of a graph drawn between cut-off voltage and frequency of incident light in a photoelectric experiment is

The de-Broglie wavelength of an electron accelerated between two plates having a potential difference of 900 V is nearly