The wave nature of the electron was verified by_____.

In an experiment on photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be $4.12\times {10}^{-15} \mathrm{V} \mathrm{s}$. Calculate the value of Planck’s constant.

What is the de Broglie wavelength of a ball of mass $0.060 \mathrm{Kg}$ moving at a speed of $1.0 \mathrm{m}/\mathrm{s}$?

What is the de Broglie wavelength of a dust particle of mass $1.0\times {10}^{-9} \mathrm{Kg}$ drifting with a speed of $2.2 \mathrm{m}/\mathrm{s}$?