Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material, photoelectric current is emitted. If the frequency of light is halved and intensity is doubled, the photoelectric current becomes -

zero times the original current

$v_1=1.5v_0$

$v_2=\frac{v_1}{2}=0.75\,v_0<v_0$

⇒ photoelectric effect (P.E.E.) not possible.