When a metallic surface is illuminated with radiation of wavelength $\lambda$, the stopping potential is $V$. If the same surface is illuminated with radiation of wavelength $2 \lambda$, the stopping potential is $\frac{V}{4}$. The threshold wavelength for the metallic surface is :

Question

( A ) $5 \lambda$
( B ) $3 \lambda$
( C ) $\frac{5}{2} \lambda$
( D ) $4 \lambda$