Q 12-11-137JEE MainJEE Main 2021 (27 Aug, Shift 2)Medium
A monochromatic neon lamp with wavelength of $670.5$ nm illuminates a photo-sensitive material which has a stopping voltage of $0.48$ V. What will be the stopping voltage if the source light is changed with another source of wavelength of $474.6$ nm?
Answer: (C) $1.25$ V
Using $hc \approx 1240$ eV nm:
$E_1 = \dfrac{1240}{670.5} = 1.85$ eV, so $\phi = 1.85 - 0.48 = 1.37$ eV.
$E_2 = \dfrac{1240}{474.6} = 2.61$ eV, so $V_s = 2.61 - 1.37 \approx 1.25$ V.
Solution by Sreeraj P, M.Sc Physics