When radiation of wavelength λ is used to illuminate a metallic surface, the stopping potential is V. When the same surface is illuminated with…

When radiation of wavelength $\displaystyle \lambda$ is used to illuminate a metallic surface, the stopping potential is V. When the same surface is illuminated with radiation of wavelength $\displaystyle 3 \lambda$, the stopping potential is $\displaystyle \frac{\mathrm{V}}{4}$. If the threshold wavelength for the metallic surface is $\displaystyle \mathrm{n} \lambda$ then value of n will be \_\_\_\_.