When photons incident on a photosensitive material of work function 1.5 eV, the maximum velocity of the emitted photoelectrons is $8\times10^5$ ms$^{-1}$. The stopping potential of the photoelectrons is (Mass of the electron $= 9\times10^{-31}$ kg and charge of the electron $= 1.6\times10^{-19}$ C)
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The stopping potential $V_s$ is directly related to the maximum kinetic energy of photoelectrons by $K_{max} = eV_s$. $K_{max}$ can be found either from the electron's velocity ($1/2 mv_{max}^2$) or from Einstein's photoelectric equation ($K_{max} = hf - \phi$). Choose the appropriate formula based on the given information.